Page menu not displaying properly in IE

I am pretty new to using WordPress and have set up a site using Atahualpa. All looks great until I came up against a problem with the dropdown page menu not working properly in IE6, IE7, AOL (says its IE8) and other Trident-based browsers. What happens is the second and third levels do not display, or they display and some text disappears. Mostly you can get the text back by hovering over but not always.

I was initially using the new WP menu system but came across a post on the BFA forum that said Atahualpa didn’t support them – though that was some time back – but I tried reverting back to just using the standard page menu. No difference.

I am using Ata 3.6.7 on WP 3.1.2 with BuddyPress 1.2.8 and BuddyPress Template Pack 1.0.2 and a few other plugins. I have tried switching most off and on and have also tested on a BP-free site but still get the problem.

In addition I have some other problems with elements not rendering properly in IE etc. such as a widget/form to link to Mail Chimp. Is the common thread in my problems jquery?

Across all browsers the dropdown slides behind some page elements such as flickr and WP-Cumulus.

Any help would be very welcome. Thanks in anticipation.