I also experimented with http:// protocol and the same error message. I have spent last 2 days just working on these issues and here is what I would like to summarize:
1. Repositories created on shared network drive with 1.6.12 subversion engine (svnadmin) or 1.6.10 TSVN, will not commit through TSVN or even through a Linux svn client. The error message is: svn: Commit failed (details follow): svn: Couldn't perform atomic initialization 2. Repositories created on shared network drive with 1.5 subversion engine (svnadmin) will work fine including committing. So the question is why would repositories on shared network drive will work if they are created with 1.5 subversion engine and will not work if they are created with 1.6? Is this a bug?