Allroad suspension dropping

I bought an 01 allroad about 6 months ago with 100k on it. When I park the car, it drops down as low as it will go. When the car is started, the assending light comes on and flashes untill the previous level is attained. Sometimes, however, the light continues to flash and the car bounces down the road like a basketball - the yellow up/down light in the cluster will be flashing. This obviously, is not supposed to happen. It seems I have a leak or something in the system - does the car have to go to an Audi dealer? Is there a simple diagnostic procedure? what may I be looking at for costs? I have owned many Audi quattros in the past and have maintained them myself without problems - This allroad is a totally different Animal!