We recently upgraded to BES 4.1.5 and have started seeing strange incident and not sure if they are BES related or not.

We are seeing incidents where, people make calendar appointments in Outlook and these meetings after awhile disappear from their Outlook Calendars subsequently from HH's too. There is no pattern so far found but the problems seems to have started after the upgrade.

Have anyone seen this behaviour under 4.1.5 ?

Have you made any progress to solve this issue. I am having exactly the same issue. Our environment is a exchange 2003/2007, outlook 2007 and BES 4.1.5. We upgraded a month ago and a few users have run into this issue. I am not sure if BES could be the cause but it seems concidental that the problem appear around the same time when BES was upgraded.
Please let me know if you have found any leads about this issue.