Okay, I've never had any trouble with chromeless pop-up's before, but all of a sudden (no matter what page I go to that uses them) they just will not work right for me.
Instead of opening to whatever dimensions the creator specified, they always open full-screen now. T-T

It's so terribly frustrating... does anyone know why this is happening, or how to stop it?

have you installed any service packs for Windows XP? I believe they are the cause of that problem, and the only thing you could do to fix it is to uninstall the service packs, and anyone else viewing the site would have to do the same for them to display properly. however, they should still work fine on Windows 9x, or on XP without service packs.