Now I have a new problem and I can't figure out where to start. Whereas last time my wifes older machine wasn't affected, this time her newer machine with Windows 7 isn't affected - it's only mine - so I assume the problem is with my machine, but as per last time, the result could still be the router at work.
The problem though is different. When I login at work (home's fine with the same settings - but work has a different router - we use Testra's cable internet at work - connect through ) I connect to the network (peer network to access printer and my wife's machine) and to the internet. I can use Firefox fine. But Thunderbird does not access the internet. It's been doing this for the last week or so. We've reset the router and that makes no difference. We've tried connecting via wireless - but that doesn't solve the problem either. Exiting from Thunderbird and restarting it does seem to work - but can't swear at this stage it always works.
This morning I was comparing my settings with my wife's. and discovered we haven't actually changed her settings. We changed mine a while ago to use DHCP - previously we were using manual addresses with two different IP addresses so we could move between home and work ISP's. However I had occasion to switch to automatic so I could access another system, and have been using it ever since. I thought we'd changed my wife's settings similarly - but it's still on manual.
So I'm wondering what I do next. Does anyone have any ideas on anything simple I might have done wrong? I assume this router couldn't also be on the fritz - it is not as old as the old home one was.