I and my spouse are in the US for the entire year in 2008. From January 2008 till Sept 2008 I will be earning income on OPT Status. From Oct 2008 till Dec 2008, I will work on H1 B status (about 92 days).
If I wait for about 5-months in 2009 to complete SPT in 2009 and then file joint return as resident with my spouse (in order to be able to claim standard deduction and personal exemption for both of us) then will social security and medicare be payable for the period that we were both on OPT in 2008?

Sorry to bother you again but I want to make sure that I don’t make any errors… Thanks for your kind advise.

Yes, you can file resident tax return after you complete SPT in 2008. During OPT, your income is not subject to FICA taxes, and don't do any thing about this when you file your resident tax return.