I have upgraded my TortoiseSVN from 1.7.1 to the most current one, 1.7.6. This error does not happen anymore. So it was a bug inside TortoiseSVN and it has been fixed.
One side issue, in my previous version, (I don't remember exactly how I installed), there is svn.exe inside bin/ directory. I like to use it on Cygwin command line. But now, svn.exe is not there any more. I have to use svn on Window Explorer, which is fine, but not my preferred way. Google says it is correct that svn.exe is not available in TortoiseSVN. But I indeed had it. A bit confused.
