Version:            (using KDE KDE 3.5.4)
Installed from:    Ubuntu Packages

the easiest way to demonstrate:
when you download something from sourceforge it gives you a list of mirrors, select a mirror and it gives you a direct link for the file on the mirror webserver.
immediately click this link, and a save-dialogue pops up. don't do anything and wait until the javascript to check if the mirror actually has the file pops up another save-dialogue for the same file. so if you clicked the link they indicated before, then you have 2 popups for saving the same file. if you click abort on either one of these, konqueror crashes.
reproducible with kde 3.5.3 and 3.5.4 on ubuntu dapper 6.06 lts