Leupold, thanks for your patience. 

What I have now done is  run a file comparison between the 4.4.1 Install package and the install I am having problems with installing some core modules.  Excluding the third party module folders.  All the .vb files in the site match the ones in the install package.  I have also compared the dlls in the `\bin folder and all the 'DotNetNuke.xxxxxx..." ones also match what is in the install package (excluding any of the module ones).

With the .dll files I am still having some problems understanding this.   In this case I am not seeing any DotNetNuke.Modules.XML.dll in the ~\bin directory. An example might help.

The site had an older version of the core XML module installed.  I am wanting to upgrade this to the latest version.  (As the older version doesn't use the 'App_Code' folders should I be first uninstalling the older version?  This doesn't seem right as it would remove any instances of the module already on the pages of the site.) I take the XML module core package and install it using the Host|Module Definitions|Add new Module. the module installs and no errors are indicated.  I then click the 'return' link  and the next page I see is the Runtime Error page with the compilation error.  Am I doing something wrong?

TIA

Antony

Picked the wrong module as an example .   I am getting the same error after installing the Survey, Help or Reports modules following the same process.  Looks like I am having issues with any module that requires Asp.Net 2 and uses the ~\App_Code folders.

Antony