I've just sort of dealt with this problem in the past, but I've decided to really need to get to the bottom of it. It seems that no matter what I do, what settings I use, or what audio i put in, whenever Ableton attempts to warp it, it sounds god-awful. Little glitches, jumps, and static is everywhere; even if the track is within a measly 10 bpm or something.
I'm forced to use other programs to stretch a sample to the BPM I want it, then import it to Ableton and turn Warping off, because, even if its already at the correct BPM, it still manages to screw it up (albeit not a lot, but enough to bother me) and suck up my spare processing power.
I really don't want to keep warping off because it turns off some key features I'd love to utilize and make my life easier.
Is this a bug or what? My processor is a mid-range i5. Not great, but should be good enough to warp something when nothing else is playing at least. Especially when Traktor can stretch audio and keep the pitch perfectly on a live basis even at ridiculous BPM differences.