The same happened to me when I installed the update patch for PD8. Luckily I had the original install disc on CD, so removed the lot and did a fresh basic install without the patch. It worked much better again.
I'm now using the basic version of PD9, and although I'm aware there are updates I'm not going to install them, especially after reading your message, as I only do simple edits, and can do without what's on the updates.
Maybe remove, and start over again :
Trevor . . My YouTube site . . (Bristol, UK) . . My JVC GZ-HM1 Camcorder