http://bugs.winehq.org/show_bug.cgi?id=28213
--- Comment #4 from A Wine user RandomAccountName@mail.com 2011-09-08 03:59:11 CDT --- I tried running it manually, after letting the IE8 installer run until the point of the hang and then killing it (so the files to copy would be in place), and sure enough, cmd never exits on its own.
After running the command without 2>nul 1>nul, I see that cmd is waiting for an answer to "Overwrite C:\windows\ie8\spuninst\spuninst.exe.manifest (Y/N)?"