This has been seen with the FW Solo in Pro Tools M-powered version 7. After changing the control panel's sync source from internal to external the cursor no longer moves in Pro Tools upon playback despite the fact that input and playback can still be heard. Essentially the cursor freezes up completely until you quit and relaunch Pro Tools. Resetting the control panel does not help. During playback, the main and sub counters freeze up as well.

According to Digidesign, This is normal behavior. Pg 16 of the M-Powered getting started guide says to close PT before making changes to this control panel.