What, if anything, have you installed that may have to do with your phone's virtual keyboard, or inputs in general? Did you install any custom keyboard files? Did you remap any keyboards? Have you used ukeyboard or ukbcreator? Have you installed any of the SCIM components.

And more importantly, have you rebooted, then seen if the problem is still the same, and have you tested this in more than one or two programs. IE, if you can't get caps-lock in browser, go to X-Term, test there, go to notes, test there, go to some random custom app with text, test there. Etc. If you people don't give details about what's happened on your system recently, even if we wanted to spend our time doing all the work in figuring out your N900 bugs (which we typically do - we're masochistic like that), we can't if you don't give us details.

It's like emailing a doctor and saying "my arm hurts. Help!" And then when they ask you about how it hurts, where on your arm, and what you did beforehand, you just don't reply, go ask some other doctor, or give the most minimalistic answer possible.

Caps/Fn -lock not working is a symptom. One symptom. It can be caused by thousands of causes. If you don't specify what you recently installed, and/or what you recently did, what system files you edited, if any, etc, we can't help you except for throw out general suggestions.