Line 680 of the getmail.php file (in the 'cron' folder) tries to instantiate a new 'Item' object, but the Item class has not been made available to the script. Which, of course, makes the script die a horrible death.

Adding

load_class( 'items/model/_item.class.php', 'Item' );

to the configuration portion of the script fixes the problem.

EDIT: It seems it's only broken on Windows Servers/Machines. The functionality works in Linux "out of the box" so to speak. Will check to see if it is specific to PHP on Windows (or if it's just something wrong with my install).