If you run a traceroute to an external site, are the pings bad?
If you can PM me your username then I can check to see if interleaving's enabled on your line and turn it off for you if you'd like?
Edit: Scrap that, I think I can see what the problem was. Looks like the router we upgraded last night has been having some problems. This will have meant that the other pipes were more congested:
We've raised a problem on this and I'll look at getting a Service Status posting out.