Just bought a used 2004 GXP. I noticed a day ago that the Engine Temp Gauge has become misaligned--it'* pointing straight down. Today, the speedometer has frozen at 70 MPH after slowly ratcheting up through the day.

Are these problems likely related, or independent? Mechanical or electrical?

This sounds to me like it is very likely a failure of the cluster. The needles are moved using servo motors and there are known issues with these. You may be looking at a swap. These aren't really common to find, although you can check eBay and www.car-part.com for a nearby wrecker that might have one. Otherwise there are some companies you can send it in to for repair. Dealer is likely your last choice since the cost is likely > $1000.00.

Thank you. The car is still under full warranty for the next two months so--back to the dealer I guess.

My 1995 Bonneville just died big time--the rear control arm snapped off while driving. Messy.