MEK will do it. MEK is also highly carcinogenic. Be careful when using the stuff.

I've had reasonable luck with super glue (of all things). I don't know which particular supplier I was using or if a solvent was an ingredient. I had a problem with some cracks on a camera recently, and the stuff melted and rebonded the plastic "rivets" that held the case together. Worked like a charm.

Peace,

Drew