Another image upload error

I’m in no way well versed in php programming and all this stuff. I know my way around basic things, and I’ve upgraded my wordpress blog twice. With that said I have no idea how to fix this. I’ve deleted all the files, uploaded them. Done this twice. When I went to the new 2.5, everything works except the image uploading. I’ve deactivated the plugins, still nothing.

It crunches and I get this:

“Fatal error: Call to undefined function: wp_constrain_dimensions() in htdocs/blog/wp-admin/includes/image.php on line 173”

Then on the Gallery link I see that the image is supposed to be there because I see how it changes from “Gallery” to “Gallery (1)”. When I click on the Gallery to see the newly uploaded image I get this other error:

“Fatal error: Call to undefined function: image_downsize() in htdocs/blog/wp-includes/post.php on line 2326”

I appreciate any and all help.
Thank you!