Usergroups and styles

[Delw]

I am running v3.6.3 with a few mods installed, when I goto change a to a different primary user group the styles get all messed up most of the nav bar is missing and all the text on the forums turn white( in explorer, in firefox it pushes my lower nav bar to the right)

it looks like it is useing the stock styles. in parts of it?

if I make it so they get a secondary usergroup I have no problems, it only happens under a primary user group.
this includes the banned user group coppa user group and a few others. unregisted, awaiting email confirmation and registered user groups have no problems.
one of the members today mentioned he was seeing the white text, he was never moved to a user group or anything, Ive logged in as test register user on 4 different pcs and cannot duplicate the registered users problem.


I've included attachments for the banned user group( as an example) .
same user in the banned group, one screenshot is using firefox, the other screen shot is using explorer


Where do I start looking?
the website is http://www.azbasszone.com


Thanks
Delw