I'm using GURU 1.6.12 on a MacBook running OSX 10.6.7. When I start the standalone version with a USB MIDI controller (Swissonic) plugged in, it crashes on startup. I thought this was fixed in v1.6 beta, I already tried reinstalling etc.
Hmm, there used to be a bug with some Akai controllers but that got fixed. Try launching Audio Midi Setup (OSX/Utilities), then delete the entry for your midi controller (in the Midi window). Then launch Guru, then plug your controller back into the laptop.