Get the full version, not the trial.
I'm on a mac and I have the same Issue. I am not running the trial I have purchased the full version. Tried re-installing and this did not solve the issue. Seems like a bug in Adobe's updater software. Been on hold waiting for an Adobe Rep for the last half hour. VERY ANNOYING.
There have been reports of issues where PrPro has reverted to trial, usually after an update. Now, I do not recall hearing of this on the Mac, but I cannot think of why the platform would make a difference.
The course of action, if this has happened is to:
1.) Deactivate (likely that this will be grayed out, if it has reverted to the trial, as there is no Activation for the trial)
2.) Uninstall CS4
3.) Run Adobe Clean Script CS4 (make sure to get the Mac version), several times, rebooting between each
4.) Install CS4 and immediately Activate and update
5.) Then, Open your Project.
Hope that this helps.
So far, there does not seem to be much detail on why the full-paid version does the revert thing.