I would definitely uninstall and then reinstall the software.
I would also go to Windows Update manually to ensure I have all of the latest (even the non-critical) updates and ensure that I have the latest version of Quicktime from Apple.
I too had the same issue - along with an inability to (re)open video projects. I did a few things.
As long as I created the project using the DV - "Standard 48kHz" setting, it worked. Selecting "Widescreen 48kHz" allowed me to save the project but I was unable to open it, receiving the error you are getting about needing to use Pro.
The second issue is an inability to open an existing project. Premiere launches, a progress bar shows "loading....1%...100%" - then nothing happens. The workspace is empty and all menu options are disabled.
First - install 8.01, and reboot! The installer doesn't indicate that you need to. I continued to have the same problems until I rebooted.
Second - upgraded the ATI drivers from the Dell website. Apparently my 2-week old Dell XPS-16/i7 laptop came with drivers from 2009 - go figure.
To recap, 8.01 (+reboot) fixed the "need Pro to open" issue
Updating ATI driver from Dell website fixed the "can't open existing project" issue.
And while on the Dell website you'll notice lots of drivers that need updating. I did them all.
upgraded the ATI drivers from the Dell website. Apparently my 2-week old Dell XPS-16/i7 laptop came with drivers from 2009 - go figure.
This is very common. The driver install discs are usually done about once per year, if that often. The same for other companies, and not just Dell. When my custom builder does a new computer, the first thing that I do is install all the latest drivers, as even he is behind the curve.
With programs, like PrE, the app. will interface much more closely with the audio and video drivers, than almost any other program you can use. If those drivers are not up to date, then problems WILL occur.