patch that works on a mac crashes on a pc

I've got a patch which I've tested fairly extensively. It's basically a sample playback unit, that uses MIDI file playback to trigger samples with poly~. Everything works fine on the Mac version.
The windows version, which is exactly the same (except its on a windows machine) crashes. It consistently crashes (the app quits, rest of os is fine) only after the audio is turned on, and when a midi file starts playing-- sometimes 15 seconds into playing, other times only 2 or 3 seconds in.It always crashes.

I've tried a number of drivers in the dsp setup window, and messed about with the various settings each driver has. I've changed drivers and hardware output to a digi002, a tascam dm3200 using the IF-FW/DM firewire card, and haVE bypassed all the fancy hardware that's here (turned it all off)and use the headphone out minijack of the computer, but the behaviour does not change. Before it crashes the audio is finely rendered in living stereo, no distortion or anything.
It doesn't crash when I manually trigger samples, which is another feature of the patch. If audio is left turned on without playing samples it doesn't crash.

Another odd thing-- I've incorporated the dsp setup patch and SOMETIMES, but not always when an open message is sent to the dac object, a completely different window opens.

This all happened as soon as I downloaded Max and opened it up (demo version) for the first time. I've built a standalone from this patch which exibits exactly the same behaviour.

cpu usage hovers around 10% when audio is on.
No third party externals are used. File paths are correct.
Any ideas out there? Am I missing something obvious? What might or could it be (all suggestions, no matter how remotely relevant will be gratefully received...)

Help.

specs are:
OS Name    Microsoft Windows XP Professional
Processor    x86 Family 6 Model 15 Stepping 6 GenuineIntel ~2394 Mhz
Total Physical Memory    2,048.00 MB