Sounds suspiciously like one or more of the pressure sensors has stopped checking in. Although I'm not 100% certain, I believe you can use the screen to display the pressure in each tire. If you have a bad sensor, it should be pretty easy to spot. Otherwise, take it in to the dealer and let them plug in the diagnostic computer and find out.

__________________
"It's not about how fast you can go, but how well you can go fast."

Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles