DataAssist should just be executing a simple INSERT or UPDATE sql statement and redirecting to the details page.
Perhaps it is having trouble displaying the details page? Can you navigate to the details page easily? It also starts and uses a Session variable to keep track of the newly inserted or updated ID, perhaps it is a problem with that, although you imply that eCart works, which uses the session so if it has no problems, then it is doubtful.
I am sure there is nothing that DataAssist is doing or that you have done in dataassist that would cause this problem. In the years it has been out this problem has not been reported, so it is likely a problem with your configuration.
Did this help? Tips are appreciated...
