Hi fellas, newbie here

My problem is rather unique, specially because up until a week ago it wasn't there!!!
I've been experiencing annoying frame loss problems when capturing video. But last week, I captured everything I wanted to at 29.97 with no frame loss whatsoever. Why am I having this problem? Why now and not last week? It's probably not rejection to my Star trek tapes (or so I hope). I've already defrag'd my HD and tried pretty much everything that's suggested to avoid frame loss (DMA is alerady on, preview is off, etc...)
the videos I captured last week went so smooth you could hardly tell they were digitalized. Now, I get to see the USS Voyager making a bumpy flight at 21, 22 fps.

Here's some interesting info that may or may not be connected:
the Pinnacle software installation was never completed smoothly. When the Assistant was running its final test, it would freeze my pc (black screen) at the overlay test. Still, the capturing worked alright despite all that up until this weekend. Also, the pinnacle driver doesn't show on VirtualDub's list (it never did), but then again, it wasn't a problem last week. Why now and what do I do.
Also, the CPU usage is hardly above 30%. What could be causing this lossin that case? It could even be higher, I don't mind, as long and I could really capture like I did last week (I'm thinking of trying to capture the same tapes to see if it actually *is* something about the tape I'm using now)