I ran into a similar problem, I figured I'd post just in case someone else runs into this. My issue was with the property svn:externals.
When I contact support, they asked me to e-mail them the svn:externals that I has set. When I copied and pasted the values (in TSVN, each was on it's own line); but, when I pasted into a text file, there were extra CR LF characters, even though then did not display as such in TSVN. When I removed the extra CR LF characters, pasted it back into TSVN, my issue was resolved.
