Mozilla stops accepting typed input

["Martin J. Hillyer" <mhillyer@marincounty.net>]

I'm having an irritating problem with Mozilla.  After what appears to
be a random length of time (often very short, eg, after one entry), it
stops accepting typing in, for example, the address box, or in a
google text input area.  I have to kill that instance and start
another to get it to accept typed input.  Clicking on links still
works normally.  Does anyone have any ideas?  

I've thought that perhaps I'd remove a config file and let it
reconfigure, but I don't see any obvious rc files - 'locate mozillarc'
only gives /etc/mozilla/mozillarc, which has only one line.  Nothing
obvious pops out from my ~/.mozilla directory - there's a binary file
in there called appreg, and two folders - /fonts, and
/<my_logon_name>; the latter only has the rather mysteriously named
folder /b3nzixf2.slt, which has lots of stuff relating to bookmarks,
cookies, etc, but nothing seems to stand out as possibly corrupted.
Nothing I've looked for in Google has turned up any clues, so I'm
turning to the list...

I'm running testing, kernel 2.4.20, X 4.2.1 with an Athlon XP1500+,
512 MB RAM and an nVidia GeForce2/MX-400 64MB video card.  I have been
bitten by the AMD-AGP issue, but this seems to be pretty much under
control with the 2.4.20 kernel (it was a problem through 2.4.18).

Please hold suggestions that I use a different browser; I know that
(and I've used various), but I would like to get this Mozilla problem
fixed because I like its many features (popups, cookie and login
management, eg).

Thanks for any ideas...
-- 
Martin Hillyer