Help trouble-shoot high CPU usage

[bnam]

When I first installed GBPVR a week or so ago, the CPU usage was about 35-40% vs. the Fusion v3.11 I was running which was (and is) about 40-45%.

Then for some reason CPU usage on GB-PVR went up to 80-85% in LiveTV mode.
And now there is a distinct stutter in many channels.

I've tried different settings to no avail.

My system:
Dell Dim 8300 P4 2.8 800FSB with HT (though I'd turned HT off)
128MB Geforce 5200 8x AGP with Aperture at 128
512MB DDR2 400 memory
WinXP with all upgrades
Fusion 5 Gold+ (watch only OTA HD)

Without GB-PVR on, CPU usage is <5%

Config settings:
Video Decoder ZuluBDAHDTV or Nvidea (no real diff between the 2)
VMR9 (I tried overlay -- there was some but not substantial improvement)
on Misc tab:
Live preview unchecked (I've tried checked with passthru and unchecked)
MS-DVR for Mux

What else should I try?

Thanks,
Byas

[sub]

It might be worth looking in the gbpvr.exe-native.log. You might not be using the video decoder you think you're using. Sometimes directshow refuses to use the one you've specified and uses another uninstead.

Post the log file and I'll take a look.