For information on build numbers, versions and release dates, please refer to the KB article KB001421: K2 Product Releases and Build Numbers. That article also contains links to the release notes for each release.
You can use the Windows Control Panel's Programs feature to retrieve a list of the installed K2 components and their versions. For details on how to do this on various operating systems, please see the KB article KB001893: How to determine the installed K2 software version, updates and fix packs.
Determine the version number of K2 components installed on each machine, and then ensure that all the components have the same number (for example 4.16060.2000.1). In the case of distributed installs, you will need to check each machine where a K2 component is installed.
To correct a system that uses a combination of versions, perform an installation or upgrade of the latest or required version for the components on the machines with the incorrect version numbers.
If K2 assemblies (for example SourceCode.HostClientAPI.dll, SourceCode.Workflow.Client.dll, SourceCode.SmartObjects.Client.dll and others) have been manually distributed to machines or servers, those .dlls also need to be updated to the same version as the version on the target K2 server environments. Failure to do so may result in errors like "Invalid archive type".