Firefox switches windows when summoned from kmail

There seems to be a bug in the interaction among Firefox, KDE, kmail, and OpenSUSE 11.0, and I don’t know where to turn to get it resolved. I’m running KDE with 10 desktops. Assume I have started up Firefox on Desktop 2 and kmail is running on Desktop 1. I then click on a link in a kmail message. When I do that, the Firefox window moves from Desktop 2 to Desktop 1, overlaying kmail and hiding my mail messages. The link target shows up in another tab, as it should. In kcontrol, I’ve specified the browser as firefox -new-tab.

Before I switched to OpenSUSE 11.0, this behaved as it should – Firefox remained on Desktop 2 when the new tab opened. Now it doesn’t.