Toxic mortgages - what's going on?

Several proposals for alleviating the mortgage melt down include re-negotiating the terms of the loans. Some would allow bankruptcy judges to set new terms that a troubled homeowner could meet, thereby avoiding foreclosure. The homeowner gets to keep his house; the bank avoids the expense of foreclosing and selling the property at a loss; the neighborhood avoids the stigma of obvious foreclosure signs and notices with the resulting general collapse of home prices, leading to still more foreclosures. It seems to be a very positive solution to a terrible financial crisis that is spiraling out of control.

However, these solutions are going nowhere. Evidently, part of the problem is that no one knows who owns the "toxic" mortgages, so all lending institutions are tainted. Thousands of mortgages have been bundled and shares of the bundles sold to investors, so the actual owner of a mortgage might be hundreds of people or entities. Today's NY Times says,

"The securities are complex and hard to evaluate, and there is little public information about precisely which assets are owned by each bank. And some prospective purchasers say banks are not making many available for sale, or have refused to accept the prices being offered."

I don't understand how this can be such a hurdle. You can damn well bet that if a homeowner pays his mortgage someone takes his money, cashes the check and distributes the funds to someone who owns the mortgage. The organizations in that chain of custody know precisely who gets what portion of the mortgage payment. How can it be that in trying to negotiate the loan, the owners of the mortgage cannot be precisely determined? What am I missing? Is this simply more obfuscation? Who's in charge here?