Bluetooth Troubles -- ATT Blackberry Bold 9000

I recently took delivery of Gen III Prius V that I love. The car drives even better than I recall from a fairly quick test drive while the electronics package (I have the navigation system but not the AT package) compares favorably to two much more expensive European cars that I own.

My only challenge so far has been with my ATT Blackberry Bold / 9000 and the car's bluetooth phone system. The problem is that although the Blackberry links readily to the system, the in-dash phone keypad lights up and then shuts off (goes dark) every few minutes -- ie, sometimes I can use the dash / navigation screen keypad to make calls and sometimes I cannot. This happens only while I am driving.

The weird thing is that the Blackberry is linked at all times to the bluetooth system (regardless of whether the dash keypad is dark) and I can always make a call via the system by using the keypad on the handset. I can also receive calls on the system at all times -- regardless of whether the in-dash keys are lit.

I believe the car's bluetooth system is fine given that my wife's iPhone 3G links perfectly while the Blackberry in question has always linked without a problem to a variety of Motorola ear-pieces that I have used.

Any insight / experience that someone could offer to this phone nuisance would be much appreciated.