What's the name of the zip that you're trying to check in, and roughly how big is it?
Thanks for the response. The name of the package is GSE702ENL.zip and it is 123MB.
Ah, OK - that makes sense: this is the entire GSE install package as opposed to an extension. (You can add some extensions by pointing ePO at the install package, but the GSE package is a bit too big for this.)
Try extracting the zip to a temp folder: in the GroupShield folder you'll find GROUPSHD7000_0409.zip and GSE7REPORTS.zip, Check these in one at a time and you should be fine.
Oh, great! That worked.