Will foreign lending make up for all the losses in the subprime catastrophe? How much will it take?

There is no way to 'make it up'. Investment portfolio's, whether it be loans, collection accounts, stocks, and so on, have a beta. Beta is considered the risk relative to the market. Subprimes were risky, because they were high risk loans(loans are investments). You take that risk anytime you have investments. Goldman Sachs was smart enough to leverage their position, which minimized the risk relative to the earnings expected.