Sounds like it`s siezed up. recommend pulling the whole rear suspenion and disassemble and check all the piovots/shafts and anything that moves for freedom of movement and go from there. You can view service repair manual in the general forum I think. it will give you a chance to grease everthing and it`s a good time to change the slides
Can you take some photos of it? When you say no travel, do you mean limited travel or no movement at all? What's the overall condition of the sled, you're not posting much detail which makes your question kind of hard to answer.
It could be that just the shocks are frozen. When they get water in them, they will not move once they get cold. You have to pull the rear skid out, anyway, so like the others have said, service the rear skid.
i was looking at some measurement tonight and i think somebody has put the proaction in wrong. i only have about half inch travel and tunnel is cracked around bolts. this sled runs great and isnt in bad shape so i will put a litle more time and effort in fixing it right. thanx for the replys when i get it done ill try to post pics