When you say "it showed up fine" - you mean that you were/are able to upload a picture and insert it into the post with the default theme, but with the wp-andreas01 theme, you can't?
Sorry to harp on it - but if you change the theme back to the default, are you able to do everything fine? This is just such an unlikely thing to have happen with a theme change, so I'm wondering if it is a problem that simply cropped up at the same time.
If it IS a theme problem, the theme must be using a variable or overwriting a value that is messing up the upload.
What version of WP are you using, and what version is wp-andreas01 certified for? Does the theme provider have a forum or comment list where you can ask for help there?
If you can't resolve it, I'd consider changing the theme - from looking at the URL, its a fairly basic layout. Beautiful to be sure, but a lot of that is your great banner.
Maybe something like vSlider would work for you? Just trying to think out of the box a bit.
Good luck!
Cheers,
A