Portal speed, admin versus normal users

We have the expressportal 5.2.1 running. Even with no user load, we can see
a big difference in loading of the portal pages, between admin members, and
normal users. Even with not much content on the pages. We think it is a
problem since we imported 30000 documents. It isn't doing any ldap requests
for page loading, so that doesn't seem the problem. I traced the (Oracle)sql
requests, but that wasn't so much either, and the sql replys were fast.
When I have a standard user and promote him to be portal admin, things speed
up.

Paul