I have set the "when firefox starts" and "home page" values, but when I reboot the computer (or more accurately, when I restart the computer as it has been crashing frequently of late), those values get reset to some default value which I don't want.

If I close Firefox then reopen, the correct values appear.

How I do store the values over reboots?

The values are

when firefox starts: show a blank page 
home page: about:blank

I'm still using Windows XP so there's no problem about directory permissions.