I am 100% positive that this is due to the way the modules have been related through custom code, but I am not positive of what the report is expecting here.

When I try to build a matrix report for a custom module (built from scratch under 5.0), I get the following error:
Fatal error: Report::require_once() [function.require]: Failed opening required '' (include_path='C:\wamp\www\current\include/..;.;C:\php5\pear') in C:\wamp\www\current\modules\Reports\Report.php on line 540

Unfortunately, I am not sure what resource the report is looking for. Is it looking for the Ext2 relationship from the vardef, is it expecting a file that doesn't exist, how do I move forward to troubleshoot this sisue?