Very useful information, thanks a lot. I have windows vista (x32) OS and when I had upgraded quicktime player to 7.7.3 version became to the same problem like you described above. Just that I wanted to open one movie file in photoshop CS4. I found QTCF.dll in C:WindowsSystem32 and draged it to the desktop. And it worked !! :)
Now I put QTCF.dll in the recycle bin but I didn't empty it yet. Photoshop still works like it should. Now i have another question, Is this old QTCF.dll file could be in use with some other programs or can I remove it freely from the computer?