assertion failed (svn_dirent_is_absolute(local_abspath)) in SVN 1.7 beta

Using TortoiseSVN 1.7.0 beta 2 on WinXP SP3:

TortoiseSVN 1.6.99, Build 21735 - 32 Bit , 2011/07/28 20:35:52
Subversion 1.7.0, -dev
apr 1.4.5
apr-utils 1.3.12
neon 0.29.6
OpenSSL 1.0.0d 8 Feb 2011
zlib 1.2.5)

I was in the middle of merging a few revisions from trunk to a branch (using the "Merge a range of revisions" option), got conflicts on two files and resolved them using TortoiseMerge, then clicking on the "Resolved" button. I then got a conflict on a third file, resolved that in TortoiseMerge, but after I exited TortoiseMerge and clicked on the "Resolved" button, I got the following assertion failure:

---------------------------
Subversion Exception!
---------------------------
Subversion encountered a serious problem.
Please take the time to report this on the Subversion mailing list
(users_at_subversion.apache.org)
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:

In file
 'D:\Development\SVN\Releases\TortoiseSVN-1.7-beta2\ext\subversion\subversion\libsvn_wc\wc_db.c'
 line 1481: assertion failed (svn_dirent_is_absolute(local_abspath))
---------------------------
OK
---------------------------

-- 
Name: Dave Huang         |  Mammal, mammal / their names are called /
INet: khym_at_azeotrope.org |  they raise a paw / the bat, the cat /
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