How to tackle debugging a plugin problem

I have come from a CI background and this is my first EE 2 site. I have posted a few questions on how to get the ED Imageresizer plugin to work, mainly on this post :

http://ellislab.com/forums/viewthread/155253/#751349

No one has been able to help me but a few have tried so I am going to try and tackle the debugging myself. I would appreciate if anyone can give me a few pointers of how to try and debug the error below :

I have updated to the most recent build of EE today and ran the install wizard and rest of the site seems ok.

A PHP Error was encountered

Severity: Notice

Message: Undefined property: Ed_imageresizer::$EE

Filename: ed_imageresizer/pi.ed_imageresizer.php

Line Number: 72
A PHP Error was encountered

Severity: Notice

Message: Trying to get property of non-object

Filename: ed_imageresizer/pi.ed_imageresizer.php

Line Number: 72

Fatal error: Call to a member function library() on a non-object in /var/www/vhosts/gunkdesign.co.uk/httpdocs/system/expressionengine/third_party/ed_imageresizer/pi.ed_imageresizer.php on line 72