Reg T Margin account question

[hoffmas 13]

I have a question for the Reg T experts...

I currently have two Reg T margin accounts with Interactive.  To make it as simple an example as I can... let's just say they each have $50K in them.  I want to use margin to buy $50K of stocks plus up to $50K of options in each account.  

In account 1 I own $50K of stock and it will then let me open additional stock and/or option positions (can purchase on margin).  

In account 2 I own $50K of options positions and it will then not let me open any additional stock or option positions (can not purchase anything on margin).

The net position of the two accounts would be the same  ($50K of stocks + $50K of options) but the order in which I purchase them makes a difference.  Is this the way Reg-T really works or am I missing something?  

Thanks.

[Marco 223]

I don't put my self in the 'Reg-T margin expert' bucket but here my *guess* on what's happening:

a/c1: you buy $50K worth of stock. Stocks a marginable securities, usually Reg-T allows for 50% margin. That leaves you with 25k buying power to buy further stock or option positions.
a/c2: you buy 50k USD worth of options (I assume that means you are long options or option spreads where you maximum loss is the premium you have spend). Options are NOT marginable securities. So your buying power is now zero and you cannot make any further purchases.

even in account 1 you should not be able to buy 50k +50k but just 50k Stocks plus 25k of options