Assertion failed!

This keeps popping up when I try running the cleanup command.
---------------------------
Subversion Exception!
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Subversion encountered a serious problem.
Please take the time to report this on the Subversion mailing list
with as much information as possible about what
you were trying to do.
But please first search the mailing list archives for the error message
to avoid reporting the same problem repeatedly.
You can find the mailing list archives at
http://subversion.apache.org/mailing-lists.html

Subversion reported the following
(you can copy the content of this dialog
to the clipboard using Ctrl-C):

In file
'D:\Development\SVN\Releases\TortoiseSVN-1.7.1\ext\subversion\subversion\libsvn_wc\workqueue.c'
line 672: assertion failed (checksum != NULL)
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OK
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[SMT]

Alex Jackson
Platform Software Engineer
919 493 9390 (main)
919 354 4725 (direct)
919 200 3568 (cell)
a.jackson_at_smt.com
www.smt.com<http://www.smt.com>