actually the title of your post is very correct fragles
it is indeed a windows live mail bug and not a kmeleon bug.
they don't know about other gecko browsers
and so if they don't see firefox they don't work.
you can change the useragent to firefox before visiting hotmail(tools menu>user agent>firefox)
and a better alternative so you don't have to change the agent everytime you got to hotmail is to use the auto agent switcher extension which will detect when you fo to hotmail and automatically change the agent for you
you can download autoagent switch from this page:
extract the 7z package in kmeleon folder and restart kmeleon..click on tools>useragent and check autoswitcher to activate it