Here's a problem I came across, in case anyone else sees it.

When upgrading a K2 Blackpearl 0803 project that involved infopath and sharepoint, to 4.5, I couldn't compile.  Kept getting the following error:

Error 1 The URL is not a valid format. 

Parameter name: url C:...Application.msbuild 79 6  

Error 2 The URL is not a valid format. 

Parameter name: url 

C:...Application.msbuild 80 6 

At its root it was the issue documented here: #mce_temp_url# 

I had a new 'default sharepoint site url' of type 'Sharepoint Site URL', and an existing Automated_Process variable of type 'miscellaneous field'. Both set to http://app1:91 which is the location of the sharepoint site in this sandbox environment. 

I'd changed the Automated_Process variable to type 'sharepoint site URL'. However when I looked again this change had not 'taken' and would not take. Whenever I changed type and saved, the environment variable would revert to 'miscelaneous field'. 

Deleting both environment variables, and creating one new variable, name Automated_Process, type Sharepoint Site URL, set as default, fixed this problem.