In reply to a post by daamon:

Thanks MrSaffron. What would you expect a sensible MTU setting to be? My connection says its 100Mbps. Can the MTU be set through Windows 7 or is it set directly on the device(s)?

My setup is telephone jack through a filter into a modem then network cable to my laptop. This is exactly the same setup before I moved and nothing's (knowingly) changed in terms of settings on the modem and laptop. Why would the MTU change to be potentially causing this problem?

I've launched the command prompt and run the command "netsh interface ipv4 show subinterfaces" and it shows that all interfaces, including the Local Area Connection has MTU=1,500.

From Googling, this appears to be the default. Should it be another setting?

Thanks.

Problem solved.

The cause and solution: I moved to a new place and my phone line was through a new exchange, so a new telephone number. The UW userIDs incorporate the phone number, so the "old" userID was no longer valid.

I popped the new userID and password directly into my modem's settings and all is good.

Thank you guys for your input.

Thomson modem - they make many models, but usually the ones with a network cable are a router.

Tell us model number.

In reply to a post by MrSaffron:

Thomson modem - they make many models, but usually the ones with a network cable are a router.

Tell us model number.

It's the ST510 v6.

But I've found and fixed the problem - it was a credentials issue. Thanks for your help though.

1500 is usually good.

What are the online testers actually seeing your connection as using.

Strange that they should allow partial access.

Some other providers when this happens present you with an obvious, your details are wrong web page.

Yeah, that's what threw me - it was working, but only for non-secure traffic. I took it as some setting or something blocking secure traffic.

Still, with the suggestions you guys provided it pointed me in the right direction to check MTU and DNS settings and I spotted my old telephone number in the userID on the router and tried that - voila!

And my MTU is set to 1500 and all's fine.

Thanks again.