Performance problem on Macbook Pro

[Palli-Moon]

I bought a brand new Core2Duo MacBook Pro about 2 weeks ago, I'm very happy with it. But, finally today I bought myself a upgrade to pro tools 7.3. Everything seems to be fine at first but when I start records I get the H/W buffer error though I'm just recording 1 mono audio channel. I admit I don't get it as frequently when I change the buffer to 1024 samples, but still I find it kind of strange that this computer can't record a single mono channel at 256 samples, I even get the error when I try to listen to the 50 sec of audio I managed to record before I got the error. I tried monotoring the CPU load and it doesn't seem to go high at all, it's at about 2% and doesn't even move when I get the error.

I'm using a MBP Core2Duo with the classic Mbox.

P.S. And yes, I tried using the usb port on the left hand side of the computer

[DigiTechSupt]

Please start with the steps in the OS X Setup and General Troubleshooting sticky at the top of this forum, especially those areas on trashing preference and database files.