The result of the problem depends of the configurations. However, the problem seems to be related to OMS 2.3.1 (ships with Pro Tools 4.0). OMS 2.3.2 works properly.If the problem is still running with OMS 2.3.2, open the OMS Studio Setup, check the configuration as described in the manual, and verify that the " 1mHz " & " Has Synchronizer " are active by clicking on the MIDI port item on the left of " std midi interface." Also, verify that "Use Serial DMA..." is disabled in OMS.