7.4.2 LE AIR products drop-out (Polyphony?)

[Paul PT]

Hi guys,
I have a 17"Mac Book Pro 2.6GHz with 2GB RAM - Running 7.4.2 Using the AIR instruments with the M-Audio Axiom.

I seem to have a problem with polyphony... When I hold more than 4 or 5 notes down at the same time using - for eg a patch in Hybrid - the notes cut out. The more notes I hold - the worse the problem.
I sometimes get a window suggesting that I should change the buffer size etc - but the computer is running at the optomem speeds - and it is a powerfull computer. (I have changed the settings but get the same probs)
This problem happens with only 1 active instrument and midi track with no plug-ins.

Can anyone help please?