Help!

Firstly, I've never had any problems with opening animated gif files. (And yes, I'm doing it in the right way: File > Import > Video Frames to Layers) but suddenly I've become unable to open the files while this notice appears:


I use Adobe Photoshop CS3 and I DO have QuickTime (7.6) installed. I just don't get what's wrong with it. Anyone?

Thanks in advance!