I am on the tail end of a 2003 to 2007 migration. The last nagging issue is the OAB on outlook 2003 clients. At this point I have not uninstalled the exchange 2003 however I do have the server turned off. In the organization configuration and in OAB there are 2 OAB 1 which is the legacy OAB from the 2003 server and the 2007 OAB the 2007 OAB is set as the default and I do have client support support for 98,2003,2003 sp2 checked off. I also have enable web distribution and enable public folder distribution enabled.When the 2003 clients do a send and receive they get a sync issue on the OAB Task 'Microsoft Exchange Server' reported error (0x8004010F) : 'The operation failed. An object could not be found.'The 2007 clients are not having any issues with the OAB everything for them is working fine. I am not sure where to go to resolve the issue before I uninstall and decommision the 2003 server.

I beleive I found my answer in http://support.microsoft.com/default.aspx/kb/905813 after checking I did find that each of the data stores were pointing to the legacy OAB and not the new 2007 OAB. I changed them to point to the 2007 OAB and it resolved the issue. Funny that changing the new OAB to the default did not change the datastores.