- Click start and Run
- Now type the following: regsvr32 softpub.dll and press enter
- Restart MSN Messenger
To be sure repeat the step above with the following lines.
regsvr32 wintrust.dll
regsvr32 initpki.dll
regsvr32 MSXML3.dll
"Sorry, we were unable to sign you in to the MSN Messenger at this time. Please try again later.
To let us try and troubleshoot the problem, click the Troubleshoot button."

#1 Wrong time/date
Set the time right. This could solve the this problem.