buffer size with reason and protools

[dj_prolifik]

I am running Protools 6.4 LE (via the original mbox) on an Emac OS 10.3.8 with 1gb of ram and a 1ghz processor. The program has been running fine for nearly two years. I recently introduced reason 3.0 as an auxiliary track to add synth information from Reason to pre-existing Protools sessions. The Reason signal is registering in the Protools auxiliary track, I am able to hear the Reason information through a headphone jack in the mbox, and midi information is appearing on a track within Reason. In essence, everything is fine with one important exception. Ten seconds into recording, the session is halted by an error message within Protools telling me to increase the H/W Buffer Size. When I increase the H/W Buffer Size and begin recording the session is again halted by another message asking me to decrease the Buffer Size.

I have tried many different combinations of H/W buffer and Playback Buffer within Protools. I have also decreased the CPU usage limit within the Reason preferences. What can I do? Any suggestions would be greatly appreciated.