Thank you for reporting this issue.
The message box you describe appears when an exception is thrown from GetTypes() for some of the assemblies that VisualStudio references. These assemblies can be plugins (Resharper, for example), or assemblies that you are referencing in your projects.
We made several tests in-house and found that, for example, Resharper assemblies are causing that message box to appear. Of course, in your case the assemblies may be different.
We completely agree that no message boxes should be shown for failures with third party assemblies. This issue will be further examined and fixed. In the upcoming release, the message box will show the assembly name and more details about the exception.
If we could be of any further assistance, please do not hesitate to contact us.
the Telerik team