- Copy the file away
- svn revert FILENAME (in case you have local changes)
- svn rm FILENAME
- svn ci -m "Fixing checksum mismatch"
- Copy the file back
- svn add FILENAME
- svn ci -m "Fixed checksum mismatch"
All the info I found addressing this contains way too much cruft and doesn't present the actual solution clearly. Here are steps that will work, so you can get back to coding: