Here's one that deserves a post.
A client was having a sporadic problem with files becoming locked or marked read when they tried to save them on their Small Business Server. The problem seemed to be much more prevalent with extremely large files. Thinking it was something with the server we move all the data to another server and remapped everyone's drives to the new server. The problem continued to exists. Okay it's either a network problem or a desktop issue. Even with a brand new fresh XP build with all service packs the problem existed. Alright! It must be a network problem. Lets just replace the switch and we will be done with it. Nope..... The problem still existed. Now we are scratching our heads. After numerous testing scenarios we realize that when a workstation first boots up it was going out and grabbing random files on the network share. What could be causing this? It turns out that Windows Desktop Search tool was configured to scan the mapped network drives. This inherently is not a bad thing, unless you have ten workstations doing this. What was causing files to get locked so people couldn't save them was when most applications save an open file they create a temp file to write all the changes to and then merge the temp file with the original file. The problem turned out to be when a user clicked save and the temp file was created there were nine other workstation just ready and waiting to index that new file. If any workstation was indexing the temp file when the application wanted to merge the data into the original file the app would throw and error that the file was locked by another user and could not be saved. The reason it was more frequent in large files is because they take longer to save; there for the temp file sits there longer and has a better chance of being indexed. We disabled the indexing of the network share and file saves are working great now.