Can't Change Header Image

Hi,

i downloaded and installed blogs-mu and have it displaying properly on my site. one exception, i can't change the header image. after i got all the image colors reconfigured to match the theme, it won't display when specified. and i see the file is uploaded to the media area, good copy of it.

firefox, ie, safari, refreshing, ctrl+f5 when possible. it's not there. all i see is the blogs-mu image with a link to my homepage.

now, another thing to throw in the mix is that earlier in the day, i believe wp super cache was hanging things up a bit. from my pc, my site looked great. i tried from another pc and it was plain text, no colors, terrible. i edited content on the site, refreshed on my pc and it looked great with the new content, while the other pc still showed it all text. i disabled wp super cache and then was able to browse on the "bad" pc. maybe a stylesheet got stuck in cache?

any ideas? the header's the main issue for me.

thanks!
Jason