I think this error ultimately comes from me not having xdelta installed correctly on my machine. Still it would be nice to trap these and put to the moodle log with a decent message

Notice: Undefined index: different in C:\projects\VLE\Mobile Moodle\environments\xampplite-win32-1.6.6.exe\development\offlinemoodle-0.3\htdocs\moodle\lib\xdelta.class.php on line 284

Notice: Undefined index: different in C:\projects\VLE\Mobile Moodle\environments\xampplite-win32-1.6.6.exe\development\offlinemoodle-0.3\htdocs\moodle\lib\xdelta.class.php on line 81