I had a similar intermittant stability issue with my 97 Cad back in 2002. I got some sort of message stating a stability control fault. I also got the "vehicle speed limited to 97 miles per hour" message. (Bummer!) No warning lights at all.
Turned out to be a bad BCM (brake control module).
It was replaced under ext warranty first time around and no more faults for 22K miles so farr. It may have had some cold solder joints in it.
(I bet i just jinxed myself there...)

__________________
-Rob Young
1972 Cutlass Supreme Convertible (442 clone) -"Lady" (My mistress...)
http://www.flickr.com/photos/robsalbum/sets/
1986 Cutlass Supreme Coupe - "Pristine"
1978 Ford (Old Faithful) a.k.a. "the Tramp"
1997 Cadillac STS (for sale - too many cars!)
1999 Harley Davidson Sportster - "the Freedom Machine"