I found the googlemail POP troubleshooter at:
which didn't actually help on this occasion (came up with a problem that it couldn't resolve - invited me to send a message outlining the problem which generated an automatic response suggesting I use the troubleshooter)
i ran the autoconfiguration tool another couple of times, in sheer frustration. I'm now in the interesting position of having two identical accounts set up in outlook express which are both my default account. it then started working properly, ho humm
i'm not closing this thread yet as it's an intermittent fault so I'll need to see if it continues to behave.