I've just this minute discovered the magic that is MixMeister BPM Analyser
Drag&drop tracks into its main window ans it calculates the bpm VERY accurately.
Then just turn off the "auto wap long samples" option in the "Defaults" page of preferences in Live and enter the bpm manually in the sample box.
I've dropped 10's of tracks of known bpm including some of my own and including beatless stuff and it got it right every time. Disregard the last decimal place and ur laughin.
I'm doin a mashup now right now and i wanted to sample a track for which i didn't have the bpm - it told me 104.01 so i put it in Live as 104 and its perfect. Its a long track with beats all the way thru, so I let it run its whole length and scrutinised the timing of every shot for teeny tiny indescrepencies, but nope, it's spot on.
Hope this helps - maybe this is commom knowledge and I'm looking really slooooooow right now

