This error could be as simple as a reboot of the exchange server and or the Add2Exchange replication Server.  Seriously, Try that first please.

If that works we will stop the Add2Exchange service and then proceed to limit the amount of SQL memory we use from the option “Minimize Memory Footprint” from the A2E Toolbox, with the Add2Exchange Service Stopped. 

This could be a simple reregister of the CDO.dll file in the directory in which it lives. In Exchange 2007 and 2010 it is in this directory [C:\Program Files\ExchangeMapi]  the command is regsvr32 “C:\Program Files\ExchangeMapi\Cdo.dll”

It is likely that a new antivirus def was applied which is stronger and getting in the way of normal operation.  Move where the CDO MMP files are being made to a new dir something like C:\Windows\MMP and then exclude from active file scanning.  http://support.diditbetter.com/kb/A2E_218.aspx

Make sure Active file scanning is off on the Directories and subdirs:  Where  A2E is installed, usually

[C:\Program Files\OpenDoor Software®] and [C:\Program Files\Microsoft SQL Server] and [C:\Program Files\ExchangeMapi] and the new mmp directory you create in the step above.

But if this failure to copy always happens on just the same items, there could be an attachment of some size which is triggering exchange to reject it.  http://support.diditbetter.com/kb/a2e_181.aspx.  Less likely, it  could be the items use a custom form and the event messages are just giving the effect that it can’t copy. http://support.diditbetter.com/Forums/Thread.aspx?pageid=1&mid=2&ItemID=1&thread=12&postid=23

You can tell from outlook viewing the source in a list type format and add the field “message Class”.

Less often while syncing and more often when opening the  console for the first time, it could be

http://support.diditbetter.com/Forums/Thread.aspx?pageid=1&mid=2&ItemID=2&thread=56&postid=120

and finally, if all else fails, could be

http://support.diditbetter.com/kb/A2E_189.aspx

Please let me know which worked for you