By default InstantKB.NET 2011 targets .NET Framework 3.5 SP1. To run InstantKB .NET 2011 under a .NET 4.0 application pool there are a few changes required to the web.config file.
To assist customers looking to runInstantKB .NET 2011 under .NET 4.0 we've provided a .NET 4.0 web.config file attached below. You should copy this web.config file into the root of yourInstantKB .NET 2011 web application folder replacing the existing web.config file.
You will need to update the database connection string to point to yourInstantKB .NET 2011 database once you apply this web.config. This should resolve any issues runningInstantKB.NET under .NET 4.0.
If you have any questions with regards to this article or using InstantForum.NET under .NET 4.0 please don't hesitate to open a support ticket