I think racquetball, contrary to popular belief, actually helped my tennis by getting some tennis related cross training with the quick movement and reflexes. I haven't ever had a problem confusing my strokes, western forehand and two hand backhand is not a whole lot like racquetball.
I used to be pretty good at table tennis (or so I thought), but then I joined a league with a bunch of older guys that just hit slice all the time. It wasn't fun because I wasn't used to it, and the older guys weren't very accepting/cool about a newcomer. I pretty much have played under 5 times in the last year.