[Xmonad] trouble with xmonad 0.3: mod-tab intermittently makes mouse clicks cease to work

I tried Xmonad 0.3 last night. I have a double-monitor setup, configured as separate screens (I used this successfully with Xmonad 0.2.) I was only using one of them, with the FullScreen layout, and a bog-standard, uncustomized, no-extensions Xmonad 0.3. Occasionally, Mod-tabbing between screens resulted in mouse clicks doing nothing -- the mouse continued to move the cursor. Cycling through the windows again with mod-tab fixed it. I can't reproduce this at will -- like I said, it's intermittent. Is anyone else facing this?