TortoiseSVN is doing its best to help you resolve the situation with the mixed revision revision working copy. If you accept the update you should get back to the commit dialog and be able to retry the commit (which should now succeed).
The same situation happen with the Subversion command line client:
[[[
$ svnadmin create ms_repo
$ svn co file:///home/daniel/ms_repo/ ms
Checked out revision 0.
$ cd ms
$ touch file1
$ svn add file1
A file1
$ svn ci file1 -m 'committing file1'
Adding file1
Transmitting file data .done
Committing transaction...
Committed revision 1.
$ svn propset svn:ignore bad.file .
property 'svn:ignore' set on '.'
$ echo "modify">file1
$ svn status
M .
M file1
$ svn ci -m 'changes'
Sending .
svn: E155011: Commit failed (details follow):
svn: E155011: Directory '/home/daniel/ms' is out of date
svn: E160028: Directory '/' is out of date
$
]]]
Above is same error as shown by TortoiseSVN when I try to commit both the changed file and the changed property. If I commit only the file, the commit succeeds.
[[[
$ svn ci file1 -m 'changes only committing file'
Sending file1
Transmitting file data .done
Committing transaction...
Committed revision 2.
$
]]]
If I'm missing out something in your reproduction receipt or what you are trying to do (for example if you are only selecting the file in step 7, then please report back in this mailing list.
Kind regards
Daniel