I'm having a similar issue:
1) When I attempt to search (or click the pod cast link on top of the page) for podcasts on the itunes store, it loads a blank screen. All of the other categories load... music, movies, books etc.
2) Also when I try to enter my account login/password, it just keeps prompting me to do it again, but it recognizes bad passwords. I can't log in to access my account settings no matter how many times I reset my password.
The weird thing is, if I log into the admin account I rarely use, itunes does not behave like this at all.