I have an SVN repository (hosted on Dreamhost) with needs-lock set on binary files. It sometimes happen that, while committing files locked and modified by me, the commit fails
I also encountered the same problem and found that out of three machines, in one of the machine I have locked the file and due to which I also facing the problem. What I did is release the lock from that machine and proceed further.
OR
Steal the lock first and then start working as this is the best option provided by SVN.