i found the solution on other thread. It works for mehope it solve it for youhttps://supportforums.cisco.com/discussion/12434491/jabber-106-invalid-certificate-issue

Hi,have you fix the issue?i m having the same issue.and performing the crappy work around by uncheck the user and check back again

I m having the same issue on Jabber 10.6it only happen on certain user.try re-install to Jabber 10.5, it works.

Hi, i'm having the same issue.have verified the options settings.all is checked, but there is no alert sound as well.anything more that i can do to Troubleshoot?