TSVN 1.5.0.13316 - Odd issue with branching working copy

I attempted to branch my working copy of our project's trunk, and got the following error (the path has been renamed to protect the innocent...) at the end of the process:

At revision: 366
Can't check path
'https://10.10.10.10/svn/MyProject/branches/temp/notDoneYet': The
filename, directory name, or volume label syntax is incorrect.

I was attempting to branch from my working copy of 'https:// 10.10.10.10/svn/MyProject/trunk', and selected the option to switch to the new branch when complete.

The branch appears to have completed successfully on the server; my working copy appears to have switched successfully, but all of the existing modifications appear as if they were never committed, preventing me from committing or updating.

Any ideas as to what my problem is?

Thanks,

--
Phil