Some have reported that the multi page content module is not providing any information to the DotNetNuke search engine, but I am sure that it is registered and is working.
I tested it a lot, used the debugger to look for anything that could go wrong, and even solved a link issue where data was on pages other than the first and the parameter was encoded to a friendly URL. But still I couldn't reproduce the reported error.
Then I installed a fresh DotNetNuke, and installed the binary version of the module - and now the reported error was true, no page content could be found with the search engine. The only difference is that the source files have been compiled into a DLL.
In the module registration page, the compiled module has no checkmarks in Portable, Searchable, and Upgradeable; in the source version the checkmarks are fine.
My first idea was that the code must have been optimized away, as I have placed all the code in a separate class which is not use by the module, only the DotNetNuke framework. So I moved all the code to the Controller class, which is used by the module and therefore cannot be optimized away, - but still no luck, the error is still there.
My next idea was that it was an issue with the site running in medium trust, so I tried in the local installation - and the error was still there, so it's not a trust issue.
It's late and I will continue tomorrow.