Problems with 002 Rack and PT6.4

[jstunner]

Hi, I'm a new user of Pro-Tools and have only been working with this for about 3 weeks. So excuse my lack of knowledge. I just got comfortable with 6.1.1 and this update has got me a bit confused. The main issue I've been having is the buffer playback setting. For some reason when I set it for 128, I get an error and a message to increase the setting. Ok, no biggie I thought I'd set it to 512. Well after about 30 seconds of playing I get the other error, and try decreasing the setting, which leaves the 256 setting, well I still get the decrease the setting error. Which leaves me with no other settings. Any idea what could be going on? I'm running Windows XP with an Intel Pentium 4 2.8 Ghz processor with 2 Seagate SATA hard drives 7200rpm and 1 gig of RAM.

PS. I went to Highschool with IntelDoc (Mr. TBR Stuidio) He's been a huge help, and will be working with me on this. The more feedback the better.

Thank you for your time.