Key System Font Missing


Hi, I need some help with a missing key font on my macbook pro. At some point last year whilst installing now fonts, I think I somehow had a font conflict, the resolution must've involved the computer deleting one of the conflicting files. Now, whenever I download a new application or make some other change to my system, and it wants to ask me for my password, the text in the message is just rectangle boxes instead of english text. It hasn't been a problem up to now because each time it came up, I knew it just wanted me to enter my password. But I need to fix this issue now because Im giving the macbook to my parents. Some help to fix this would be greatly appreciated! Thanks :D
If your "font issue" is ONLY on password entry, then I doubt that you have a missing font.
You should not ordinarily see the password as english text anyway, but will be dots, such as •••••
Could be that you have changed the text input to Extended English, and not the normal English? check that in your International pref pane (or "Language & Text" pane in Lion or newer, which will have an "Input Sources" tab, not Text Input)

If you don't make any progress with adjusting your system settings, then you may find it easier just to erase and reinstall the system, as you would usually do when selling your Mac to someone else.
I say that here, too - Erase and reinstall, so you might avoid passing along other possible problems that you might be ignoring (or forgetting)
Thanks for the reply! Sorry I meant the text in the message box, not just the password entry. Each character is a box with an A inside. But yeah, I might reinstall anyway. But I'm also thinking, if I migrate all my files onto a new Mac, am I going to migrate the problem too? I guess I just thought I might be able to find the font, and re-install it or something.
I'd say that it's not a missing font, per se.
More likely either a system setting that has gone awry (the font choice), or perhaps a font cache file (try clearing your font caches, then restart). Another method to try for those font caches is to boot into Safe Mode - Restart, while holding the Shift key. You can release the shift when you see the rotating gear. You will get an account login window, even if your system is set for automatic logic. The Safe Boot mode will take considerably longer than normal - sometimes 10 minutes or so, which is completely normal. Some system cache cleanup can take place during that boot.

You didn't say what OS X version you have.
Another possible fix is to download and reinstall your current OS X combined updater. That can often help out with fixing a variety of odd system behaviour, and takes much less time than reinstalling everything.
Again, I don't know what OS X version you have, but here's the combined updater for a Snow Leopard (OS X 10.6.x) system:
If you have another OS X version (10.5, 10.7, 10.8, etc) then just search at the Apple downloads for what you need. I can also give you a good link for another if you let me know which version you have now.

To answer your question about migration, I would doubt that a simple migration will cause the same issue on a different system. But, you probably should fix before you move on to another Mac, anyway.