Tell me more about the file system folder structure where mojoportal is located vs where the store is located and also about the IIS configuration.
Does the store folder actually exist under the mojoportal root folder?
Is the store folder configured as an application, does it have its own Web.config in the store folder, and its own store/bin folder?
Are you using url forwarding or proxying or some such?
Is it .NET 3.5 or 4.0?
What version of IIS?
What version of mojoPortal?
should also wrap system.webserver section