Pro Tools "h/w Buffer Size" Options

[theunderground]

Every once and a while in Pro Tools LE I get this message:

Audio processing is conflicting
with other CPU tasks. If this
occurs often, reducing the "H/W
Buffer Size" in the Playback
Engine Dialog may help
prevent the problem. (-9129)

I do as I am instructed, then I try pressing play and this message pops up:

The operating system held off
interrupts for too long. If this
occurs often try increason the
"H/W Buffer Size" in the
Playback Engine Dialog.
(-9094)

so I switch back the buffer size to 1024, and that usually takes care of the problem, but every once and a while it doesnt, and I get a nasty cycle between these two messages.

Im running Pro Tools LE 6.2.2 on a dual 1.8 G5 (512MB RAM) using it with Reason Adapted. This hasn't been a huge problem, but I am considering using my M-box for live shows, and that would be really bad if does that in the middle of a song. The only solution I can think of would be getting more RAM, but 512MB seems like a reasonable amount, and I am usually only working with, at tops, seven tracks.

any help is appreciated

-David Kieffer