your best bet would be to open it up and see if its a standard part (i have a feeling it is with the remote mounted either side). archos wont do anything as they have quoted to members on here that the av500 is now a legacy item and wont repair.
You could be in luck if its just a standard part that you could purchase in an normal electrical shop.
Or you may find it just got dirty contacts / dry solder joints.
Another direction you could go if that dosnt work is get a broken av400 / gmini 400 / gmini 402 / av500 and use the parts from them as i think they are basically the same setup.
roy