First of all 3300 kbps at 66% is way too low a quality for action video. If a higher setting won't fit on one DVD then I'd strongly suggest dividing the project into 2 DVD's, giving you room for something more reasonable for action shots; say 6000 kbps at 80% or better.
2 pulses a second indicates that they occur at the GOP boundaries. GOP = Group Of Pictures, the image arrangement used in MPEG files.
GOP's for DVD are "IBP" MEPEG's consisting of 1 real bitmap (an "I" frame something like a JPeg) followed by either 11 (PAL) or 14 (NTSC) calculated "B" or "P" frames.
These synthetic frames are calculated by the motion differences between the previous and next I frames and are arranged something like this (NTSC GOP's shown);
IBBPBBPBBPBBPBB IBBPBBPBBPBBPBB IBBPBBPBBPBBPBB etc. etc.
Remember: the B and P frames are mathematical constructs, they don't really "exist" which is why MPEG files are so much smaller than DV or MJPeg. They are 100% I frames.
Sometimes with action shots there is too much motion between the I frames to precisely calculate the B and P frames, often causing pulsations or other artifacts.
Plan A is what I mentioned before; divide the project and use higher quality settings. If that doesn't do it then go to Plan B.
Plan B is to modify the advanced MPEG settings to something more suitable for action shots. These changes usually fall into two catagories;
1. set the encoder to create more GOP's per second. More GOP's means fewer synthetic frames and more I frames, which are
real images.
In NTSC instead of a 15 GOP (one I frame + 14 BP frames) one might choose a 6 GOP (one I frame + 5 BP frames). This would mean instead of 2 GOP's per second there would be 5 GOP's.
2. improve the motion search precision. More precision improves the quality of these calculations at the cost of encoding time. Sometimes this is the sacrifice you make for shooting high motion video.
The specifics for both MSPro and VideoStudio are dettailed in tis tutorial;
http://forum.corel.com/EN/viewtopic.php?t=10880
VideoStudio users: read ALL of it as in the followup posts there is info specific to VideoStudio.
Good luck!!
Obviously I can go back to VBR, but I'm not even certain this issue won't raise it's ugly head there now too, as I don't know why it's happening, or if it's anything to do with CBR!!