I'm in the same boat right now. Fermentation stuck at around 1.042. I warmed the carboy up to around 74 degrees and shook it up a bit, but that didn't help.
I repitched with a couple packets of wine yeast three days ago because that's just what I had on hand, but that doesn't seem to be doing anything either.
I'm not sure where to go from here. I clearly can't bottle with the gravity this high, but I don't know how to get it down. My last resort may be to brew another batch of beer with some high gravity yeast just so I can pitch this onto the cake.