We had a double-disk failure on RAID5 array last week (yes, it does happen). One of things that got affected was our source code repository.
So, we reinstalled etch and installed subversion, did svnadmin verify on repository and all seemed well until we tried to commit using
SVN DAV. Apache's error log was full of errors like this:
Could not create activity /svn/repo/!svn/act/9526cf2d-4893-4b35-a843-4c0f2d9f8bc6. [500, #0]
could not open dbm files.