I just opened a newsgroup with about 50000 postings. It took several seconds (minutes?) before mozilla started updating its windows and taking user input again. I used my providers newsserver with a 768kbit connection. My PC is a Duron 800 with 128 MB Ram. The CPU consumption was high, around 60 %. I used mozilla-0.9.4-3mdk from Mandrake Cooker (Build ID:2001092020).
*** This bug has been marked as a duplicate of 84042 ***