"Suspend all threads while stepping" doesn't seem to do anything

I have a multithreaded app (running in tomcat, if that matters). I set breakpoints, click "Suspend all threads while stepping," a breakpoint gets hit, the debug panel flashes briefly, and then antoher thread picks up running.

I am completely unable to debug anything right now.

I searched the forums and found this question posted a couple times a few years ago, but no anwers.

Any suggestions?

(IntelliJ 6.0, btw)