If you have recently upgraded iOS6 and your IPhone devices are having issues have a look, the issue mentioned in KB2768774 and remedy is to “wait” (-: yes you have heard correctly , there has not been any fix for the issues described in the KB.
iOS6 devices erroneously take ownership of meetings
I will update the post as the workaround is available.
Oz Casey, Dedeal ( MVP north America)
MCITP (EMA), MCITP (SA)
MCSE 2003, M+, S+, MCDST
Security+, Project +, Server +