Have you tried starting the K2 service in console mode?  Console mode allows you to see what is happening in K2.

To do so, find the path to the EXE as stated in the Window services applet.  You'll want to omit any command line parameters when running in console mode.  I'd highly recommend doing a Run As... on the executable (right click on the exe in Windows Explorer and select 'Run as...").  This will allow you to execute the application under the same identity as the service.  Thus if there are any issues with this service account you'd be able to see it first hand.

Once you have console mode fired up, look for any obvious errors that are occuring within K2.

HTH.

Thank you very much for your reply :-)

But I don't find any error in particular when I start it in console mode.

Below you can find the log of the console, can anyone see the problem?

 I copied from the screen:

;K2 HostServer Console Mode
;======================================
;Loading .NET Framework v2.0.50727
;Framework loaded successfully.
;Creating App Domain.
;Creating Host Server Runtime.
;Boot Strapping Hosting Server Runtime
;Press ESC to end..

Info    1001 Host Server Started as PROOFOFCONCEPTk2service
Info    1002 Using .NET Framework v2.0.50727
Info    1003 Host Server Version: 4.7285.1.0
Info    1005 Initializing Connection to Host Server Database: Server.HostServer
Info    1007 Initialized Connection to Host Server Database: Server.HostServer
Info    1010 Enrolling Type : SourceCode.Security.Providers.K2UMProvider.K2UMProvider
Info    1010 Enrolling Type : SourceCode.Security.Providers.SalesforceProvider.SalesforceProvider
Info    1010 Enrolling Type : SourceCode.Security.Providers.SharePoint.SharePointProvider
Info    1010 Enrolling Type : SourceCode.Hosting.Server.Services.DiscoveryService
Info    1010 Enrolling Type : SourceCode.Hosting.Services.DependancyService
Info    1010 Enrolling Type : SourceCode.Hosting.Server.Services.TCPIOCPService                                                      Info    12000 Dependancy Service Initialized
Info    1010 Enrolling Type : SourceCode.Workflow.Runtime.K2LogServer
Info    1010 Enrolling Type : K2Server
Info    1010 Enrolling Type : SourceCode.Categories.Runtime.CategoryServer
Info    1010 Enrolling Type : SourceCode.Dependancy.Runtime.DependancyServer
Info    1010 Enrolling Type : SourceCode.EnvironmentSettings.Runtime.EnvironmentSettingsHostableServer
Info    1010 Enrolling Type : SourceCode.EventBus.ManagementServer.ClientServer
Info    1010 Enrolling Type : SourceCode.EventBus.Scheduler.Server.ServerImplimentation
Info    1010 Enrolling Type : SourceCode.EventBus.Scheduler.Server.ClientServerImplimentation
Info    1010 Enrolling Type : SourceCode.EventBus.Server.ClientServerImplimentation
Info    1010 Enrolling Type : SourceCode.EventBus.Server.ServerImplimentation
Info    1010 Enrolling Type : SourceCode.Hosting.Servers.LicenseManagement
Info    1010 Enrolling Type : SourceCode.Hosting.Servers.Management
Info    1010 Enrolling Type : SourceCode.Security.UserRoleManager.Runtime.UserRoleManagerServer
Info    1010 Enrolling Type : SourceCode.Hosting.Servers.SecurityManagement
Info    1010 Enrolling Type : SourceCode.SmartFunctions.Runtime.SmartFunctionEngine
Info    1010 Enrolling Type : SourceCode.SmartObjects.Runtime.SmartObjectClientServer
Info    1010 Enrolling Type : SourceCode.SmartObjects.Runtime.SmartObjectManagementServer
Info    1010 Enrolling Type : SourceCode.Workflow.Runtime.Management.WorkflowManagementHostServer
Info    5000 URM Server Initializing....
Info    5001 URM Server Initializing....
Info    5002 Default label name K2
Info    12500 Dependancy Server Initialized
Info    1005 Connecting to Host Server Database.
Info    1007 Connected to Host Server Database.
Info    1005 Connecting to Host Server Database.
Info    1007 Connected to Host Server Database.
Info    10500 SmartObject Runtime.Management Server starting up......
Info    10507 SmartObject Runtime.Management Connecting to Store Database on SERVER ....
Info    10509 SmartObject Runtime.Management successfully connected to Database on SERVER
Info    10510 SmartObject Runtime.Management Store using integrated security.
Info    10505 SmartObject Runtime.Management Server started successfully...
Info    15000 Workflow Management Server Initializing
Info    15001 Workflow Management Server Initialized
Info    1005 Connecting to Host Server Database.
Info    1007 Connected to Host Server Database.
Info    7500 Loading Eventbus Scheduling Server Version='4.0.0.0' Last Updated='06 Aug 2007 00:00:34'
Info    7523 Loading Schedule Server
Info    7505 Configuration settings initialized
Info    7532 Initialization Check Successfull
Info    7513 Service registered with ID:36 running on machine: GVA-VM-WORKFLOW
Info    7503 Loading ScheduleEventRecorder..
Info    7504 All Recorders Loaded
Info    7514 Schedule Buffers Initialized Successfully
Info    7522 Schedule Server Loaded Successfully
Info    9035 Initializing SmartFunction Engine...
Info    9040 SmartFunction Engine successfully initialized.
Info    7000 Version='4.0.0.0' 12 aout 2007 17:45:02
Info    7001 Checking EventBus Server Dependencies
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    1020 Starting Session A416054291E3095C450CB00AC2835866
Info    3000 Authenticating SHAREPOINTK2account for session A416054291E3095C450CB00AC2835866 using K2 - NTLM
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..
Info    7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded..

...

From what I've seen, the Info message "7003 SourceCode.SmartObjects.Runtime.SmartObjectClientServer not yet Loaded." can be caused by a number of things.

Take a look at the below post here to see if any applies to you (it outlines a couple of things to check):

          http://k2underground.com/forums/thread/22642.aspx

I have already checked this post :-)

Do you see anything missing in the logs? or any other suggestion?

Thanks

I resolved the problem and I think that I know what caused it.

To resolve the probleme, I completely uninstalled K2 blackpearl and then install it again. :-)

I had a problem when I reinstalled K2. In the selection of components, there was 4 components that could not be installed. When I clicked the "dependencies" button for these components, K2 was saying that .Net Framwork 2.0 and .Net Framework 3.0 was not installed but they were on my server with the according service pack 1.

So I had to uninstall both .Net Framework and install it again. And I noticed that when I install them with the Service Pack, K2 is not able to recognize them. So I had to install the .Net Framworks without the service pack.

After that the installation went smoothly and now everything is working fine.

Make sure to disable the "Windows Auto Updates", which installs the service pack for the .Net Framworks and I think that it was the reason why it stopped working at the first place.

Cheers

Vigoret