PC mouse has sticky residue on plastic?

Help - I got a "new" mouse - an old model that was discontinued a long time ago, but the mouse itself is brand new and sealed. When I opened it up, I found that the parts of the mouse which are meant to be provide grip (along the sides for instance), instead have a very sticky feel to them. It's almost like it's got some sort of coat of adhesive which is very sticky. Any ideas what could be the cause of this or what I can do about it? I bought the mouse from a seller on eBay and paid nearly $50 in shipping (was sent from the US - I'm in Australia). Thanks.