For those you you experiencing issues with corrupt files, here is a possible work around from privateNimrod in the forums.

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"I just ran into this problem using IE and came across this thread. Since no one has posted a solution I thought I'd poke around.

Apparently, IE and PHP are disagreeing about compression. I tried ghost.zip and saw a request that included

Accept-Encoding: gzip, deflate

the response included

Content-Transfer-Encoding: binary
Content-Disposition: attachment; filename="ghost.zip"; .... ; size=16844
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 168824

What I received was a file named ghost.zip that was 168824 bytes long instead of the 16844 bytes. I renamed it to ghost.zip.gz and then unziped it. The resulting ghost.zip unzips just fine. Apparently, IE is not understanding the part of the headers that indicate that the file was sent as gzipped.

Can't say if that's everyone else's problem, but that seems to solve things for me."