The whole issue could also be related to different versions of quicktime (or whatever is ussed for decompressing mp3s on the machine) on PA and Laptop.
Make sure you use exactly the same versions on your machines. Then there shouldn't be further issueds.
LIVE 5.2 - I give up (with MP3s)
MP3 never worked for me
I have to agree MP3 is a feature that never worked for me. I seldom use Live for DJ'ing, working with ALS's with dozens of carefully-warped MP3 files. Everytime Live resamples them for whichever reason (version change, computer change) the warp points become a real mess. I think Ableton could easyly workaround this just auto-translating the file to WAV (in fact this is already done) and completely unlinking it from the MP3 file. This way maybe you'll run into problems the first time but never again. If I save a song self-contained I do prefer the giant, pre-rendered WAV files, as it gives me extra-security that things will remain the same over time. It is really painful to open an ALS file with hundreds of hours of work and see it all broken.