Hi Virtual Money,
Let me try and initiate a somewhat more adult conversation with you about your question, in contrast to the some of the responses you received on the message board.
Let me first say that this is a common dilemma and you are not alone. Especially now, when the credit markets are crazy you have every right to be concerned, I know I am.
You don't quite fall into the big boys category, yet you aren't planning on opening a 400 buck retail fx account. This puts you into a bit of a gray zone.
I am currently looking into Dukascopy.com, since they allow for a Bank Guarantee (20% kept at the broker, 80% at a bank). They are unique in the fact that you can have a BG with only 250k. Usually this would require a 7 figure account with other brokers.
Oanda states clearly on their website that in the event of default, clients may not be able to get their money back.
IB does seem to have some good protection procedures. Read this carefully and make sure this also applies to the FOREX:
http://www.interactivebrokers.com/en/general/education/faqs/safetyFAQ.php?ib_entity=llc
As far as going by who is well capitalized, Refco was well capitalized and all went wrong for spot fx account holders. They were only general creditors.
Then there is the option of fx futures. What I don't like about them is that some of the pairs I like to trade are very illiquid in their futures form (since, as you know, futures are usually initiated by parties that want to hand business risk to somebody else. So if there is no business necessity like with the EUR/AUD there will be no offers.) But they are centrally cleared and Refco futures account holders came out fine.
Fx is still the wild west of trading and in a way immature. I am still on the look up for a better deal.
If somebody couldn't give you a half-way good answer, it is because they had no clue about this. It is still a novel area.
Good luck and all the best.
scexglobal