Scheduled job 'mail_report' does not run - throws invalid error message

NOTE: I had to fix the api_action name provided in civicrm_data.tpl (was 'mail_reports' and should be 'mail_report') - so you'll need to fix that before testing this. I've updated civicrm_data.tpl and added fix to Upgrade/incremental/sql/4.1.beta3.mysql.tpl)

To recreate:

• Edit the sample Contribution Summary Report (instance 6) to that Email Delivery Settings are populated (Subject and Email Address)
• Edit the Scheduled Job to pass version=3 and instanceId=6

This "should" work based on my review of the code in CRM_Report_Utils_Report::processReport(). However, instead I get this result in the Job Log:
=========
Finished execution of Mail Reports with result: Failure, Error message: Could not find valid value for instanceId:

Parameters raw:
version=3
instanceId=6

Parameters parsed:
a:2:

{s:7:"version";s:1:"3";s:10:"instanceId";s:1:"6";}