Just a wild guess, but you mention that Drive *and* using the telephone caused reboots, and your syslog has errors related to csd (modem) saying "Internal modem communication error" *and* nped (location services) saying I/O error when reading from the i2c bus (gps, I bet).

So, again this is a wild guess, your modem chip (which I bet contains the GPS as well) is either broken or has a loose contact (reminds me of the famous "All telephony functions disabled" on the N900).

If that's the case, you need to get the N9 repaired.

I would anyway try a reflash first!