I've been getting this message for about a week now.   It seems to be hung up on some build transactions so, I delete them and recreate them although their doesn't seem to be anything wrong with them.

If I move the dates on the builds, it just picks up another  one to bomb out on.

QODBC messages reports a "non unique TXnID" for one of the build assemblies. 

I upgraded to the latest version and now I can't run it at all.   It asks me for a key# ???   and gives a "not authorized" message.

IsAService: False
Begin Session Failed. S0000 00000 [QODBC] QB Begin Session Failed. Error = 80040421, This application is not allowed to change its authentication preferences unless QuickBooks is running with the Administrator logged in.
Begin Session errors can be caused when running ASP or other system service and not setting the "Advanced" button option of either "Use DCOM Servers" or "Remote Connector"

See: How do I setup QODBC to auto-login into QuickBooks and start it if it's not running? for the changes in the authentication methods, and login into QuickBooks as the "Admin" account to do the amendments. The Advanced tab in QODBC Setup v6 Build 148 and later now has new defaults for Integrated Application Defaults Authorization popup settings. These settings are only available to USA QuickBooks 2005 and USA QuickBooks 2006 users, otherwise they are greyed out. Use these settings to allow "auto-login" with or without a visible QuickBooks User Interface.

As far as the optimizer is concerned check that the build assemlies can be queried correctly when using the UNOPTIMIZED tag as shown at: How do I setup the QODBC Optimizer? Where are the Optimizer options?