[xmonad] How to diagnose programs not launching?

I have a key set to runOrRaise "firefox3". Recently, it stopped working and I can't figure out why. Running firefox3 manually from the shell works fine, just not the shortcut. Is there a way to see what errors xmonad is receiving when it tries to run the command? I already tried looking at .xmonad/xmonad.errors, it just says: on the commandline: Warning: -no-recomp is deprecated: Use -fforce-recomp instead Which I suspect is related to xmonad rather than my firefox call.