Check your security settings. If they have changed to the highest level, you may not be able to connect as IE will refuse any connections. Also, I'd check the firewall, you didn't mention whether or not you were using the MS SP-2 firewall or a third party FW. If you don't disable the MS FW while using the third party FW, that can cause problems too. If you are just using the MS FW, check its security settings as well.
Jim W.