wrongfullyaccuzd

My girlfriend has a 2001 Stratus, only owner, and it has weird problems not 3 years later. Once it got cold this year (in like November), her car started doing funny things. We were driving to a movie one night and suddenly she says "I'm going zero miles per hour." Sure enough, her speedometer wasn't registering. Neither was her gas gauge. We stopped the car and she turned it off and on again and waited for something to register. It didn't, so we decided to drive back to her house and get my car. Suddenly, the speedometer jumped to 120 and back down to normal again. She says since then this has happened on 66 (the highway) a couple times. A couple days ago we were on our way somewhere and the needle was just going crazy, up and down, up and down. Right now it's resting just below zero, trying to go past it...at, effectively, ~200 mph.
Bad circuitry? Bad Dodge engineering? Bad luck? The cold? What's goin on?