Okay, well without seeing an example, it sounds like you're panning too fast. Video employing inter-frame compression (e.g., AVCHD or HDV) will not cope particularly well with fast pans. Not much you can do about it, I'm afraid. Even a faster shutter speed won't help (can in fact make it even more apparent by reducing the amount of blurring).
It seems odd that the issue is not apparent on a television screen. Is it a plasma or a CRT? High definition video will often look pretty bogus while you're working with it in the preview window of your editor, but if you deinterlace it upon export then much of the cringeworthiness should be ironed out.
That issue aside, let's consider the more important issue of moving the camera quickly. I don't mean to preach, but as with any tool you need to work within its limits once you've established what they are. With most consumer camcorders, especially the highly-compressed high definition formats, that means panning slowly, avoiding scenes with complex motion, and avoiding fast cross-frame motion (i.e. objects entering at one side of the frame exiting at the other in less than a second) as much as possible. The SD5 records at 13Mb per second and at that level things like fast panning and side-to-side object motion are often too much of a challenge for such a camera.
If you avoid these kinds of things, you'll be much happier with the quality of your pictures.
Best of luck,
Andrew.
P.S. The SD5 has excellent manual control of shutter speed and iris. Experiment with different manual exposure settings to see if you can find something that works better. All camcorders are more limited when used in auto mode only. Get to grips with manual exposure and you'll get more out of your videos.
