I have two background images: one for the header, one that repeats centereed lengthwise down the page, leaving a blank background of blue behind it that is visible along the edges. (Just see the site: http://www.derekbeck.com/1775/ )

I've discovered that in Internet Explorer 8 (and I've witnessed it in Google Chrome too but can't duplicate it) that if I start the page in a window that is maximized, and then resize the window to a width narrower than the repeating background image, everything moves over as it should, to center in the new smaller IE8 window, including the top non-repeating background image. However, the repeating background image that goes down the page slowly slides into its proper position.

Perhaps Related: in all browsers, if you size down to narrower than this repeating background image, and then scroll to the right, over to that part of the page not visible, the repeating background image is also messed up.

Any ideas on what is causing this?

I applied these 2 backgrounds based on this thread's suggestions:
http://forum.bytesforall.com/showthread.php?t=10932

I've attached my exported settings for those that want to see. I'm using WP 3.0.4 and ATA 3.5.3.

Thanks,
Derek

disable all plugins and see what happens

That was it... the "Let it Snow" plugin Version 2.0 | By Aen Tan... too bad, I liked it. Thx, Derek