My background:
BS - 2000 - 2004 (india)
Work Exp. - 2004 - 2008 (india)
MS - August 2008 - December 2010 (US).
Completed MS degree requrmnts - september 22, 2010.
Received EAD from USCIS for post OPT - 09/15/10 - 07/31/2011
Starting working again - october 2010 in US.
H1B Petition filed and approved - November 2010

My company applying for PERM states that since
i have started working from october 2010 before my graduation date december 2010. I'm not eligible to submit PERM with MS degree in EB2.
I have USCIS approved OPT to work legally from october 2010. Why this will be a problem while applying PERM?. How to resolve this (apart from requesting my graduate school for a letter that i have completed requirements by september 22 2010)?