Image upload problems are normally (for me anyway) file permission issues bascially the web server user does not have write access.
The warning you have posted do not describe the problem. So I would check the permissions. The only other thing i have seen is where asll images get conervted to PNGs by default that can cause problems on some machines. Try the permissions issue first though.
Good luck
Tony
Tony Wood : twitter.com/tonywood
Vision with Technology
Experts in eZ Publish consulting & development
Hug Tony, it was permission problem. What I had done was renamed a tpl file then uploaded new. Next time I will copy old first or check the permission after I do that.