I had the same problem this morning. I closed IE and relaunched and it "fixed" the problem.

>I have the problem too.
>
>~~Bonnie
>
>
>
>>Hi Michel,
>>
>>I've problems expanding the message tree. this mainly occurs if I receive the "400 messages" box. I can expand the "Category" nodes, but no other. If a Category is expandede, I can not inflate.
>>
>>This occurs since thusday last week, my first login in since my summer vacation.
>>
>>Agnes