xiaobaitu, please help me.

my I-751 is pending, 2year conditional green card expired, can i get admission into US from ooversea without any problem by I-551 stamp on my passport only? because i have never received I-751 receipt, or i must have both I-551 AND I-751 receipt? On my I-551 stamp, it states "upon endorsement, serves as temporary I-551 evidencing permanent residency for one year. Issued date: May1, 2008. Officer:****** EMPLOYMENT AUTHORIZED. Valid until: APR 30 2009"

On the stamp, it doesnt mention about travel overseas, will i have problem coming back to US?