Pro Tools 7 & Application Switching, PT7 won't play after switching apps Options

[aleman]

I'm running Pro Tools 7.0 on Tiger (10.4.3) on a mirror-drive G4 with dual 1.25 Gig processors and 512 MB of RAM. For the most part PT7 runs beautifully.

The problem I have occurs when I'm running PT7 and then switch to another application (like my internet browser, or iTunes for example). When I switch *back* to Pro Tools after using the other application, I can't play my file anymore. Any attempt to hit the "play" button (either using the spacebar or my mouse) fails.

The "play" button gets highlighted for a split second, and then the "stop" button gets highlighted immediate afterwards and PT won't play. I don't get any error messages.

It's worth noting that this does NOT happen when I switch back and forth between Reason Adapted and ProTools. It's only with my other apps.

Anyone else experience this, or have an idea what's causing it?

Thanks in advance.