http://bugs.winehq.org/show_bug.cgi?id=22286
--- Comment #5 from Dmitry Timoshkov dmitry@codeweavers.com 2010-04-06 08:59:16 --- (In reply to comment #4)
That's a hash collision, the two names will hash to the same short name. I guess you are just unlucky... If you need reliable short names you have to use a vfat filesystem.
Is this basically a wontfix?