Playback issues after some actions

[Roger Mac]

Hey guys.

I'm recording vocals for a pre-recorded track.

I've been through the "PC optimization for audio" stuff. Everything works great. Load the track, record the vocals, playback. Sounds great.

But when I try to "Pitch Shift" the sound track (-4 semitones) the track plays back slightly jerky. It's smooth and on tempo and you hear most of the track but I get "blooping" sounds about every 1/4 second. Usually have to close the app and re-open or shutdown and reboot to eliminate it.

I get the same result (without trying pitch shift) if I open the Cubase Operation Manual and then close it.

No clipping happening (according to the levels). I'm guessing maybe memory related? ?? Any suggestions?

PC running Win XP
2.25 GHz processor
512 MB memory
4 buffers at 96 kb each
defragged hard drive with 37 GB available.

Thanks.
Roger