We finally have been able to get the dlls swapped out and connect using dataport 7.4 to connect to a AbleCommerce 7.0.0 store. But now when I try to download anything, I get this.
Please post more details that what version of DataPort and API dll's you are using. Also please copy paste the version information from "Administration -> Help -> About Ablecommerce" page. I suspect its still some version mismatch issue.