Hi Beth,
Did you transfer your Web.config customizations from the old Web.config to the new one?
Maybe the error could be caused by it not having some of those customizations.
I noticed in your old Web.config you have the whole <system.web section wrapped inside a location element like this:
<location allowOverride="true">
</location>
and I also noticed these items which I don't remember every being in our Web.config so I assume it is needed for some reason on your end:
<buildProviders>
<add extension=".htm" type="System.Web.Compilation.PageBuildProvider" />
<add extension=".html" type="System.Web.Compilation.PageBuildProvider" />
</buildProviders>
<add name="PageHandlerFactory-HTML" path="*.html" verb="*" type="System.Web.UI.PageHandlerFactory" resourceType="Unspecified" preCondition="integratedMode" />
<add name="PageHandlerFactory-HTM" path="*.htm" verb="*" type="System.Web.UI.PageHandlerFactory" resourceType="Unspecified" preCondition="integratedMode" requireAccess="None" />
and also a lot of rewrite rules inside:
<rewrite>
<rules>
</rules>
</rewrite>
I would look for those things in your old Web.config and try to copy them into the same locations in the new one and see if that solves it.
The location element and the rewrite rules seem like the most likely to cause errors if missing and needed.
Best,
Joe