Frustration with Firefox extension update

[Patrick Wiseman <pwiseman@gmail.com>]

Apologies for asking here, as it's probably not specific to Debian,
but I am a Debian user (testing system) and this is a very
knowledgable group (about lots of things :).

I use the gmail notifier extension, which lets me know whether I have
new email.  But I cannot update from 0.3.3 to 0.4 - it appears to
install, but when I restart Firefox, the earlier version is still
there.  I have even uninstalled 0.3.3 and installed 0.4, but 0.3.3
comes back!  No doubt it's a permissions problem - so much with Linux
is - but I can't figure out where Firefox keeps anything so that I
could correct it.  (An aside: why does Firefox use all these random
strings for profiles and extensions, etc.?  Security through
obscurity?  It makes for a very unpleasant enduser experience, at
least for someone used to getting under the hood and editing config
files.)

I've Googled, searched Firefox help, and looked everywhere I can think
of - I can't believe I'm experiencing a unique problem, but I can't
find anything useful.  You're my last resort!

Happy new year to everyone.

Patrick