When using K-Meleon, build 0.4, I've had a problem when entering text in a text box. If I use the space bar to put a space between words, the browser causes the page to jump so that the text box moves to the top of the page. While this doesn't stop the use of the text box, the behavior is distracting. I've tested this in Mozilla builds 0.9 - 0.9.2 and none of these versions have this behavior so I think it is K-Meleon specific. An example page where you can test this is any of the search pages on this site:
Do a basic search and enter a space between two words. You should see the page jump when you use the space bar key.