Use less data :-)

In all seriousness, this isn't a Perl problem. It is most likely an MIE bug that has problems dealing with the data you send.

It's worth noting that if you are sending that many hidden fields, you almost certainly need to redsign the program and it's logic. Consider using a cookie. Hidden fields are a simple way to maintain very basic state information, and should not be used for anything you want to be secure.