The Case of the Disappearing Microsoft Sites

Last week I found Messenger suddenly stopped working. And then discover that I could not access any Microsoft sites, including Microsoft, hotmail, msn, and windows update. The message was " the server at..... takes too long.."
Other sites were OK.

My first reaction was checking the firewall setting and turning it off, running anti-virus and then turning it off, and then uninstalling it. None worked.

Could there be a virus specifically targeting Microsoft sites? Not likely, it has never been heard of.

Searching the internet, someone mentioned adjusting the MTU (maximum transmission unit)value. I did, but no avail.

I connected using a dial-up provider, but it was so slow (and Microsoft pages didn't show up, but no error message) and the results were inconclusive.

The I found this software vrle (Visual Route Lite Edition), which is actually just a fancy version of tracert, with visual and color embellishments.
It showed that after about 13 hops, there were unknown sites, packets were lost and the trace could not be completed.

So I switched to a different DNS server, namely OpenDNS recommended in the ComputerWorld article "Fix your DNS problems" , and the missing sites were back to normal!

I am still rather mystified by the whole thing, and would like to hear from others who encountered the same problem.