Go to
http://www.gamespot.com and highlight some plain (non-link) text. Right-click on it. You should notice that the "Copy Text" function is missing from the context menu. This occurs (in my experience) on all pages with background images.
Ctrl-C still works fine, but this is still a nuisance. The first few times it happened, I thought the page was using javascript or something to disable the function, but it seems to be just a k-meleon issue (mozilla handles it properly).