Hardened rubber seal on sunroof. How do I soften?

Hi
I opened the sunroof for the first time this year, no problem.
But shutting was a different matter. The roof got stuck solid half shut. When I looked the rubber seal around the glass had rucked up and wedged the glass tight. I managed to prize the rubber free only to find it has completely lost it's elasticity. It has not perished just gone hard. I am unable to seat it properly because it is so hard.
Is there any way I can soften the rubber temporarily to reposition it, i.e something I can spray on it.
Any ideas appreciated.
Thanks
Richard.