If you look up this error, some sites will tell you that it has to do with Visual Source Safe and/or a “.” prefixing a folder name.
I have visual source safe installed, but I was not using it on the particular project I was working on. I looked and I didn't have any folders with a “.” prefix (i.e. “.foobar”) contained in the project that was causing the error.
Visual Studio creates a VSWebCache Folder under “C:\Documents and Settings\username”. Find this folder and delete it. Yes, the entire folder. It's purpose is to cache folder structures (and some files) so that Visual Studio can load projects faster. It recreates itself on the next opening of a project and the error goes away. No harm done.
- Make sure Visual Studio .NET is not open.
- Navigate to Your Projects Folder (all of the places you keep projects). The two most likely places are “C:\Inetpub\wwwroot” and “C:\Documents and Settings\username\My Documents\Visual Studio Projects“.
- Enable the option to view Hidden Files and Folders. “Tools, Folder Options..., View (tab), Show hidden files and folders (click next to it), OK (click).“
- This is the fun part, and likely to take some time. Look through all of your projects and rename any folders in projects that have names that start with “.“ (period).
- Navigate to your “Documents and Settings“ folder (most likely C:\Documents and Settings) and open the folder for your username (i.e. Robz).
- Find the Folder named “VSWebCache“ and delete it.
- Reopen Visual Studio .NET and open a project.
- Verify that the VSWebCache folder has been recreated in the same place it was deleted from.
- Disable the option to view Hidden Files and Folders (if you wish). Follow the same steps as in 3, but click “Do not show hidden files and folders”.
An alternative to steps 3,4, and 9 (and to save precious time) would be to wait until the error comes back and then determine what projects are being held in the VSWebCache folder and follow steps 3,4 and 9 for just those projects in the VSWebCache. Then continue the instructions at step 5.
These instructions are for Windows XP. Directions for other OSes may differ just slightly.
The most relevant information I found came from this post: P2P Wrox Forums. Special thanks to Richard Acton for pointing this out in his blog.