won't remember gmail password

Every time the client checks for new mail I get an error box opening which insists that the gmail server is busy or my details are incorrect. When I go to “Diagnose” I get prompted for my gmail password and then both tests come up OK.
The next time it checks for mail the same happens, it seems that it’s not rembering my passord.
Any ideas at all would be helpfull, if I can’t get it fixed I’m going back to Thunderbird.