If you have a BB running OS5 like me, and, install BBM 7 which is now availible in appworld, everytime BBM does something you maybe will get an annoying pop up that the connection is not trusted (invalid certificate chain for *.voip.blackberry.com).
install 2 certifictes (should work OTA): http://www.tbs-internet.com/thawte/ThawtePCA-SS.crt
and make your BB trust it
and the second: http://www.tbs-internet.com/thawte/ThawteSSLCA.crt
Afterwards, BBM 7 should stop complaining.