Why can't my computer use yahoo services?

I have computer that is connected to internet but the funny thing all along it was working well but unfourtunately it encountered a problem:1 this comp of mine you cant use Yahoo services other wards you can't check your mails but yet it is connectint 2 internet
2. only Google is working and thereare times I can open yahoo through google and sometimes it work, so what is the problem is it my setting or what please advice.

Look for programming error(s) on your PC, and look for "Hitchhikers" with your Anti Virus. If that doesn't work, SHOUT at Microsoft!!! Then reload Windows and your MS Internet Explorer etc. etc.
Before you do that, safe all the important data on CD's.