I have a client who had to rebuild his automated build server. He checked out his project folder from my subversion server but is now no longer able to commit - he gets this error:

Error: Commit failed (details follow):  
Error: Cannot write to the prototype revision file of transaction
'551-1' because a   
Error: previous representation is currently being written by another
process  
Finished!:

I have searched Google but although this error has been often reported there is no clear explanation - does anyone on StackOverflow have a solution?

UPDATE: Nobody else commits to that repository, so it was not a transaction stuck (at least not from another user). In the end we found that permissions were not set correctly. Not that you would know it from this message, but that fixed the problem.