Kim came across a funny little error just awhile ago, and whilst trying to solve the issue, I found there to be a lack of help on the internet. So as a way to ensure that the problem can be solved with just a simple copy/pasta of the error name, I suggested we make a thread to house all solved issues. The error Kim got was: Mountfilesystem( 254 ) failed: SteamMountFileSystem(5928,254,0x1418f8d0=,0x1418f7c0) failed with error 116: Cache needs repair My first idea was that he needed to Verify the integrity of game cache for Source SDK. Turns out however, that Error #254 means that the game in question, CS:S is actually the application that needed to have its cache verified and/or defragmented. Doing a Google search of the problem however, resulted in exactly one forum, which was related to a TF2 mod, and not necessarily CS:S. Thus, if anyone is able to find a solution to a problem that is not available elsewhere, or hard to find, don't be afraid to post it, so others can easily find the way to fix problems that are otherwise harder to find / less frequent. ^^ Posted in normal color so it isn't eye raping.