This is a known problem with some ported BOINC releases, especially certain Linux x64 ports. The reason for the error is that a file (ca-bundle.crt) was omitted from the release.

If you see this error message in your message log, then you probably need to apply this fix.

• Determine your BOINC data directory. Check the beginning of your message log. There will be a line near the beginning like this:

  08/06/2007 13:18:00||Data directory: C:\Program Files\BOINC

• Download the missing file. You can get it from here: http://boinc.berkeley.edu/trac/browser/trunk/.../ca-bundle.crt?format=raw - make sure you name the file ca-bundle.crt.
  
• Place the file in your BOINC data directory.
  
• Restart BOINC. The way you do this will depend on your installation.
  

Why does this problem only affect WCG, and not other BOINC projects?
This is because WCG is (at the time of writing) the only BOINC project that requires a secure connection to the server. Other projects permit falling back to an insecure connection.

FreeBSD note: this issue has been fixed, please update your port-tree and rebuild BOINC.

OpenSUSE 11.0 Be sure to install ca-bundle.crt in the Data Directory. Just putting it in the BOINC folder is not good enough, as explained in:
http://www.worldcommunitygrid.org/forums/wcg/viewthread?thread=21418

Ubuntu Follow these specific instructions for client versions 6.2.7 and up:
https://bugs.launchpad.net/ubuntu/+source/boinc/+bug/246205

Kubuntu How to Connect Kubuntu to WCG when you get &q...rt (path? access rights?) "

Additional 'Start Here' information posted at http://www.worldcommunitygrid.org/forums/wcg/viewthread?thread=15682#121477