After restoring a SharePoint site using site template .STP files, .CMP files, or the stsadm commands import / export all data views / data forms show error messages. Web browser error: "Unable to display this Web Part. To troubleshoot the problem, open this Web page in a Windows SharePoint Services-compatible HTML editor such as Microsoft Office SharePoint Designer. If the problem persists, contact your Web server administrator."SharePoint Designer error: "The server returned a non-specific error when trying to get data from the data source. Check the format and content of your query and try again. If the problem persists, contact the server administrator."
This is a known issue, actually. We have done some work for O14 which will address this problem. The issue is caused by the incorrect ListName, which is a GUID id for the list's instance on a given site instance. We don't do GUID fix-up, and therefore the broken data views are pointing to the incorrect data source (from the old site).
I've seen several support instances with questions and concerns on this problem. Hopefully, this helps you to understand the cause of the problem, and how to fix it.