edit screen does not load

We have one user who can log in and edit their website from their office, Ipad 3G etc., but NOT from their Home PC (Win 7 Home, 64, 4 GB Ram)

When attempting to edit a page the page appears to be loading (rotating arrow) but stays like that for more than 30 minutes!

Have tried removing antivirus etc, but stll not working.

Any Clues?

J