From Bugzilla Helper: User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; 0.8.1) BuildID: 2001032904 Already opened Browser windows cannot be used, when large messages are downloaded from POP3 server. You can select the respecting process on taskbar but nothing else happens on the screen (Mail is always displayed until downloading finishes). Other Windows application work fine. It seems that Mail Back End consumes all proccesing power that can be acquired from Mozilla :( Reproducible: Always Steps to Reproduce: 1. Open 1-2 Browser windows and load a url on each of them. Wait until pages finish loading. 2. Sent yourself a message with moderately large attachment (depends on connection speed, of course). 3. When downloading message starts, try to select the Browser windows from taskbar. Actual Results: browser windows are not available until message downloading finishes. Expected Results: Being able to handle those browser instances as usual, e.g set focus on them, load new urls etc.

Pretty sure this is a dupe of something

Yes. It turns out to be a duplicate of bug 32222 (recently fixed). I tested on 2001041104 build and it works fine now. *** This bug has been marked as a duplicate of 32222 ***

verified as per reporter's comment.