I think reregistering these 3 dll files will do:
start > run > type: regsvr32 softpub.dll <enter>
start > run > type: regsvr32 initpki.dll <enter>
start > run > type: regsvr32 mssip32.dll <enter>
Now try to sign in again.
Still no luck?
Check your IE Security settings:
Open Internet Explorer, click the Tools menu, then Internet Options, then Advanced tab, scroll to the Security section, and verify that "Check for server certificate revocation" is unchecked. Also verify that 'Use SSL 2.0' and Use SSL 3.0' is checked, then click OK.
If you still can't login after that, have a look at the first two posts in
possible solutions for....
/ 
