I believe this is related to the xml documentation files.
Then copy your changes back in (don't copy any folders) and commit, and continue. One blog post with the "just checkout the entire repo again and then copy files" solution claimed that their text editor was "automatically" editing files inside the folder but I know that's not the case for me since I have that folder excluded from any global search functionality...
It seems to be a bug in SVN (plenty of which have hit me in the past); if this is truly a better CVS I can't imagine how terrible CVS must have been.
What's actaully happening to cause the svn:checksum error, and what's the best fix.
Maybe more important -- is this a symptom of a greater problem?
But honestly, your question sounds like you want us to guess what particular problem is rather than what kind of causes could cause such an error. Whether that was the cause in ur case or whether there was some other underlying issue, I can't tell of cause.