When you use ActiveSync to synchronize a mobile phone with a Microsoft Exchange Server 2007 mailbox, synchronization fails. Additionally, the mobile phone times out after several minutes.
Note This issue does not occur when you synchronize contacts or email messages with the mobile phone.
To resolve this issue, install the following update rollup:.
Description of Update Rollup 4 for Exchange Server 2007 Service Pack 3
This update rollup optimizes the implementation of object synchronization in Exchange Server.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.