[sw rec]

If it has A 7200-rpm drive, there's your problem. All audio MUST be recorded to a separate, dedicated audio hard drive. Recording to the system drive doesn't work.
Trurst us, it works, but you gotta follow the recommendations to the letter!
And I quote:

IMPORTANT! You MUST use a secondary hard drive (not your main OS drive) for recording and playback of audio in Pro Tools. Recording or playback from the OS drive is known to be problematic and the cause of many different error types. If you are using your system drive and encountering errors, the first thing you should do is get a compatible drive. USB drives are not supported and are known to be problematic, so please do not use them with Pro Tools. If you're recording or playing back from a USB drive and are getting errors in Pro Tools, please switch to using a compatible external firewire drive or internal SATA/ATA/IDE drive and disconnect the USB drive.

Pro Tools supports recording and playback to a secondary drive that meets the following requirements:

7200 rpm or faster
9ms seek time or faster