I've moved your post to the ePO community. Hopefully someone can help you soon.
I believe you may be using the wrong package for ePO check-in. There is a different version of the DAT package that needs to be used for checking into the master repository.
Click on Packages tab
Select the link "Dat package for use with McAfee Autoupdate Architect and ePO 3.0"
The filename would be something like epoxxxdat.zip
Now check-in this package into the master repository using Product or Updates option.
Hope that Helps..