Hi Tim,
I didn;t have much luck with that image. But, I did better when I cropped your 350 and then manipulated. I would have thought for a 300dpi image at 600x450 pixels it would have resized better.
Mayeb if you have a different image format otherthan jpg. Some of this artificate may be commulative once we resize. I didn't have photoshop at my disposal this morning. I'll try again later.
editted remark:
Hmm filesizes were differnet than reported in the edittor.