You might try using other methods to zip the same data set to see whether your user's Winzip 10 has any trouble with those -- and/or you might try using your perl script on a different machine. Apart from those ideas, I can only offer questions, in case you haven't considered them:

What version of Archive::Zip are you using now? (The current version on CPAN is 1.18) Note that the module reportedly depends on Compress::Zlib (current CPAN version is 2.001), so you might check that as well.

What's your OS/cpu, and how different is your user's machine? Did you get a chance to look at the Winzip 10 readme file, to check for deltas relative to Winzip 9?