Refreshing the project failed.
While working on an ASP.NET project over the weekend, I suddenly got an error message when opening my solution file:
Refreshing the project failed. Unable to retrieve folder information from the server.
I was pretty irked since I was in the home stretch of a project (you know -- the last 10% of the project takes 90% of the time!). Luckily, it wasn't that big of a problem and I was able to continue developing and debugging.
Since the problem continued, I finally googled for it and found the answer: Delete the "VSWebCache" folder in your "\Documents and Settings\[Username]" directory.