We just released an update to eCart 5 and Design Extender to address issues, the update to DataBridge will be released Tomorrow or Friday.
The new versions of eCart, Data Bridge and design Extender no longer include Memento, so any Memento error you are getting implies that you still have an older version of one of the extensions installed that may be causing conflicts. What other extensions are installed in the extension manager, including version numbers? What is the Memento error?
the type of slow down you report is not a common occurrence, and we will be happy to look into the cause with you.
Once the updates have been released, I think you will find the programs running much better, if you are running into further issues after the updates, we will look into them with you, we try very hard to make our customers satisfaction a top priority. We will extend your refund period, and if you are still unhappy after the updates have been released, we will process your refund.