Another issue with KeyGuard....
I recently got myself one of these fancy Palm Comfort Plus Hands Free Car Kit for Treo™ 680/755p for using my Treo 680 handsfree in my car.
I noticed that when I switched on power, with my Treo still asleep, something prevented the phone from connecting to the carkit (sounds still coming through the phone speaker. It drove me nuts but I discovered this: when I switch on the phone first, disable Keyguard, and then switch on the car's power, the thing works and all calls are routed to the carkit as they should. So KeyGuard is spoiling the party here!
I took me a while, before figuring this out including an unnessary hard-reset :-(.
Anyway, hope (potential) users of this carkit can profit from my experiences and solution.
Nevertheless, Palm should fix this KeyGuard problems in the next unlocked Treo 680 update...!!