are you using xport 3 or anything to split the gps signal?
If I use the GPS from the mp3car.com store (Prolific?) straight into the USB port and directly to iGuidance and iGuidance is on during hibernate, it freezes the driver or something similar. I would have to unplug and replug it in.
I use xport3 and set it to automatically reset the gps plug after resume from hibernate. solved my problem.