is the problem only w/ IE6 and 7? or is that just all that you've tried? :) on a *nix platform, you can find the portal logs at:
/var/opt/SUNWportal/logs/...
and
/var/opt/SUNWportal/portals/<portal-id>/logs/<instance-id>/...
there is also the web container log, the location of which varies depending on the vendor. for example, for SJS app server 8.2, the logs are at:
/var/opt/SUNWappserver/domains/domain1/logs/
hope this helps.