success with the AVT drivers! ..... (well maybe not... read whole reply! )
problem was this:
i run a motu 8pre with both, my pc (which has Texas Instruments firewire chip), and with my laptop (whch has via firewire chipset)
when i got the motu i tested the hell out of it, to ensure it will work with my laptop. and it worked.
it worked flawless for over 1 year. i got latencys around 5ms, so i could use amp-simulations while recording drums e.g. recorded up to 16 tracks simultaniously. and did overdubs with projects up to 30 tracks or so.
until.... well until motu announced new firmwire (1.03) and in ordr to get that, you had to update your drivers. i did and was now running driver version 3.6.8.1359.
everything went fine, except .... a noticed some crakles and the loss auf audio playback when watching youtube videos... but when working with my DAW (cubase SX3) no dropouts ever occured.
then came the day that i had to use my mobile setup again for a multitracksession, so i tried it out in advance. then realized, the old motu drivers on my laptop won't correspond with the new firmware.
so i installed the vicious 3.6.8.1400

which gave me more problems.... from now on i had more accidents of sudden clicks, cracks, pops and then high squeals than before the new driver ainstallation.
then i tried everything from setting up windows from scratch, to SP1 driver rollback, to older versions of the motu drivers (3.6.7.0 and 3.6.7.4 and 3.6.8.1394)
the problems were always there, PLUS that i now had latency issues. the software reported around 5ms of latency but it was definitely more than 40ms. you could hear it.
then i relized that on my pc i had this 3.6.8.1359 version installesd, which was the first version that came with the firmware update. i searched for it and found it still on the motu server. jsut copy the link to the new driver and change the "...1400" to ..."1359" to download it. this driver gave me back the correct latency. ...but still all of the sudden it squeals like hell.
my next step was to realize; ok... motu says their devices only work with texas instruments chips.... although i had mine working perfectly without it, it's time to realize that with new firmwire, and new driver this will no lnger be possilbe, so i should check for a pcmcia-firewire card.
i got it today, and...ahm.... that IS no pcmcia slot, but a expresscardslot... FXXX!!!! so i went back to this forum and saw THIS very thread...
i followed the instructions step by step and installed the new firewire drivers, then did that 1000cables test... for about 20 minutes long.
what can i say.....? it worked! everything was fine. no cracks no squeals no dropouts, nothing.
well the only thing is... while writing this reply, sitting at my pc, while my laptop still is connected to the motu, suddenly.... it squeals again...
my conclusion is now to return that pmcia card, get a expresscard, and try again.