This afternoon, I help my friend to fix your computer. The symptoms are no network access from internet explorer and MSN. Moreover, there is a window pop up at the startup, saying something like "mseret.dll cannot find module"(I can't remember the exact name of dll name and details of the error message). The solution is simple. We used AVG to a full system scan and removed all infected files. I found there are a number of virus in the computer. Moreover, I found the reason of no network access from internet explorer and MSN. Because the virus changed the internet connections to use an internal proxy. What I did, I went to IE->Tools->Internet Options->Connections->Local Area Network Settings->Unchecked the proxy settings. I think the virus tried to setup a proxy and force all internet connections to use that. But that computer has AVG and AVG killed the process. Thus, it makes no internet access all at all in IE and MSN. Finally, I ran regedit and search the name of dll in the error message. Then I deleted that registry to run that dll. So far, that sounds every thing is running fine now.