I nearly cried. I went to svn up in a local check out of one of the projects I’m working on, knowing that I was a good few days behind and instead of getting the usual stream of files I got an error message:
Could not read chunk delimiter
I logged on to the server and ran svnadmin verify /path/to/repo and got a different error message:
Decompression of svndiff data failed
Much googling later and I found fsfsverify.py – a script that repairs broken fsfs-type svn repositories. The author (jszakmeister) doesn’t allow comments on the page of his blog that hosts the script, so this is a public thanks for really really saving my bacon!

You’re very welcome!
It fixed my “Decompression of svndiff data failed”-problem aswell, thanks alot John!
Hmm, never mind that last post.. it fixed one revision only to find a problem on a later revision that it could not fix:
Error InvalidCompressedStream: Invalid compressed data stream at offset 4611858 (Error -3 while decompressing: incorrect data check)
I just ran into the last issue you noted as well (InvalidCompressedStream when running fsfsverify.py) – did you ever have any luck correcting or working around this issue?
Thanks!