I recently created all new stores in Exch 2010 and migrated users and the BB's are sending and receiving messages no problem. I had a user come to me with a Calender issue: updates were going from the server to the device, but not vice versa. I moved him to a different store and now he has the opposite issue: device to server works but not vice versa. I checked my calender and found that i have the issue of only server to device working. any ideas?

enable public folders?

What version CDO are you using on BES?

Double check permissions?

I ran this to apply it to the new stores

Get-MailboxDatabase | Add-ADPermission xxx8211;User xxx8220;BESAdminxxx8221; xxx8211;AccessRights ExtendedRight xxx8211;ExtendedRights Receive-As, ms-Exch-Store-Admin