[Hampshire] Firefox in Ubuntu overtyping

Hi folks,

This is a weird problem that is hard to describe (and therefore hard to
google!).

I've been running Ubuntu on my laptop for the past few years and a while ago
(ie. more than a year) started to experience what I would call "overtyping"
in the URL or Search bar in Firefox.
Basically, when you start to type a URL, after a fraction of a second it
will highlight the address bar of it's own accord and subsequent typing will
wipe out the first few letters to the point where you can only type one
letter before it re-highlights the letter and the next letter replaces it,
if that makes sense!

I've found that simply minimising and re-opening the window fixes it. It
only seems to happen when the machine resumes from standby, but it doesn't
happen every time.

At one point, I renamed my profile so Firefox would create a blank one but
after a few days, it randomly happened again. I added in the few extensions
(Adblock Plus, Delicious bookmarks and Gmail notifier) that I normally use
and copied bookmarks back over and it seems to be behaving a lot better, but
maybe once a week or so, I will get the "overtyping" when it resumes from
standby.

The reason that I've finally got around to asking about it is because I put
a completely fresh install of Ubuntu 9.10 or 9.04 (Can't remember now!) on a
laptop for my wife and the same thing started happening on her machine.
Again, when it resumes from standby and again, not reproducible on every
resume.
Admittedly, I initially copied over her Firefox profile from her windows
install but I have since blown that away and started again with a fresh
profile. I don't think she has any extensions running at the moment.

The laptops are a completely different spec, mine an ageing Compaq and hers
an aging IBM. We both have all the latest updates installed.

There is obviously more troubleshooting I could do - try a different browser
for a start, which I have done on occasion but got annoyed by all the
adverts that suddenly appear everywhere and quickly went back to using
Firefox - so I was more wondering if anyone else has seen this and found a
solution?

Thanks,
Keith.