wireless connecting - network manager problem?

[Roger Searle]

Hi, over the last month or so I have experienced increasing problems 
getting the wireless connection to connect.  This is an ubuntu 8.04 with 
gnome, network manager 0.6.6.  Only changes have been any updates via 
apt-get update/upgrade.  Connections are to 2 separate wrt54gl routers 
(home, work), set up essentially the same.   I know they function OK 
based on other laptops connecting without issue. 

Going back a month, connections would "just work" on logging on to the 
gnome desktop.  Then I would occasionally experience a problem 
connecting, and manually intervene via  network manager.  2 weeks or so 
ago I began to be prompted for the passphrase and could then 
successfully connect.  Now I am often unable to connect at all, or can 
connect after 2 or sometimes 3 or 4 times entering the passphrase.  
Sometimes I'm having to resort to an ethernet cable  :-(

Turning on and off the wireless switch on the laptop, or disabling then 
re-enabling wireless via network manager, or a reboot, or resetting the 
router, have all been tried in an attempt to resolve with any 
consistency, but generally it's random if it is successful.  Removing 
and recreating the passphrase entry in the "Passwords and Encryption 
Keys" tool (where the password is usually shown in what appears to be a 
hex format) hasn't helped.

I'm at a loss to explain what I am describing, so seeking any 
suggestions on how to resolve this or where to look.

Cheers,
Roger