At work we recently branched our code so we can work on two releases at once. For some reason the newly branched code started to behave strangely.
After I started working on the new branched code I noticed that I was no longer getting line numbers in the Error List panel from Visual Studio 2005. When multiple people are working on the same code-base its pretty hard to isolate and fix errors and warnings when you have no idea which file or line they exist. This became old quick, so I decided to try and isolate the issue. I intentionally made a compiler bug and then selectively started deleting files one by one hoping the file and line number will show for the error. I got down to only one file in the site and the situation still occurred!
For some reason I decided to copy the code and put it in another location. I was surprised when it started working correctly, but I was frustrated because I didn't know why. I got so desperate that I used Microsoft's SynchToy to synchronize my code from both folder locations. I didn't like the solution, but I was glad to have my error file and line numbers back.
It turns out that the problem was with having two parentheses in the folder name where the web project resided. The branched code we are using has two parenthesis in the name to indicate the release we are working on. To get around the issue, I just overrode my local StarTeam settings to checkout to a different folder structure and everything works fine now.
You can reference Scott's blog for more information about this Crazy Parenthesis Bug.