The rare case I have seen that were:
- incompatibility with a VM64bits (I believe this is now solve)
- due to a ClearCase update (only solution was to uninstall ClearCase, uninstall VS2010, reinstall VS2010 first, then ClearCase)
Note that this technote (originally about CCRC, which isn't your case) does mention
ClearCase and CCRC versions 7.0.1 and 7.1.1
There is no Visual Studio 2010 integration available during an installation of ClearCase or CCRC versions 7.0.1.x or 7.1.1 or 7.1.1.1.
Refer to the workaround details below for information about obtaining a utility and for instructions for setting up the integration.
WORKAROUND
A utility is available along with instructions on setting up the integration. If you have any questions or issues with using this utility, contact IBM Rational Client Support for assistance.
Refer to document 4024532 Integrate ClearCase and CCRC 7.0.1 and 7.1.1 with Visual Studio 2010 for details.
So it depends also about your exact ClearCase version.
The aforementioned technote (4024532) refers to:
When using the ClearCase integration with Visual Studio 2010, glyphs indicating the source control state for ASP.Net Web Site projects are not displayed in Solution Explorer.
(Meaning it can also depends about the type of your VS project)
The defect with Microsoft WebSite project has been fixed in Visual Studio 2010 SP1.
Visual Studio 2010 SP1 is supported from ClearCase 7.1.1.6 and 7.1.2.3 onwards.
(Meaning it also depends about the exact version of your VS itself)
Your case doesn't seem to refer to that issue, since you don't even have ClearCase contextual menu on the project files of your solution (hence my advice to uninstall everything and re-install), but illustrates the need to know the exact details about:
- the error message
- the version of ClearCase
- the version of VS2010