I tried using Internet Explorer 6 and had some weird issues with GP. I would try upgrading to Internet Explorer 7 or installing Firefox 2.0, which ever you prefer. I use Firefox 2.0 and do not have any problems using the site.
In my opinion IE7 is better IE6, but Firefox 2.0 is even better. I cannot stand the GUI to IE7 myself.
Firefox 2.0
Firefox web browser | Faster, more secure, & customizable
Internet Explorer 7
Download details: Windows Internet Explorer 7 for Windows XP SP2
Little side note: Firefox 2.0 does not replace Internet Explorer 6 or 7. You can still use IE after installing it.