spierzchala, unfortunately it sounds like you have an incompatible add-on installed.
I understand this created a bad first experience with the beta. If you decide to re-installing beta 2 you can confirm if an add-on is the problem by running internet explorer in "no add-ons mode". If the problem goes away while in this mode then one of your installed add-ons is the problem - probably a toolbar. You can find the entry point for "no add-ons mode" in the start menu under Programs-Accessories-System Tools.
If you determine it is an add-on, you can use Manage Add-ons to disable the likely candidates to narrow down the problem further.
We try our best to be compatible with as many add-ons as possible. There is a chance the issue you saw has not yet been discovered, so if you do determine which add-on is causing the problem that would be helpful information.