In the horror-comedy "Zombieland," a virtual shut-in named Columbus befriends Tallahassee, an experienced zombie killer, as the two try to survive a zombie apocalypse. The movie could be a metaphor for the proliferation of ghastly loan workouts by the nation's lenders that have created a number of "undead" mortgages.

There was a time when processing the few bad residential real estate loans was routine. Federal and state regulations require bad loans to be passed through three "cauldrons."

Troubled loans went first into a "30-89 past due" cauldron, where they cooked for up to 89 days. Many healed themselves. Unemployed borrowers found jobs, warring spouses finalized divorce papers or scatterbrained professors returned from sabbaticals.

For many years, that group never rose above the $20 billion mark for any one quarter -- a small percentage of all outstanding loans.

The mortgages that made it to the "90-day past due" pot generally were written down to reflect the underlying real estate, minus holding, selling and foreclosure costs. This holding vat generally was reduced to about 25 percent of the first group.

Finally, while a bank-owned home awaited liquidation, it could be placed in the final cauldron, the "nonaccrual" pot.

Now, fast-forward to the quarter ending in June. The 30-89 past due pot, according to FDIC data, was around $68 billion nationwide. The second pot has almost $65 billion. The third pot, about $83 billion.

The loans are not being reappraised. Many "zombie loans" represent homes in which borrowers are living, in essence, free of charge or perhaps sending a few dollars in interest to draw out the process.

This benefits the banks because they can postpone writing down toxic mortgages, which would force them to show losses and to add money to a reserve fund called a loan loss allowance, which could throw some banks into insolvency.

Final charge-offs for residential mortgages were 1.7 percent of total past due and nonaccruals in December 2004. By September 2008, they hit 14.5 percent. The rise was likely because fewer loans were healing themselves as the subprime crisis swung into high gear.

By the quarter ending in June, it had fallen to 6.4 percent. The decrease only can be due to loans not being revaluated. Our calculations put this at the equivalent of nearly 400,000 "zombie mortgages." If each accounts for one dwelling, that's 400,000 homes with borrowers being subsidized by banks.

The victim? Ultimately, the taxpayer (but more directly, purchasers of real estate and bank shareholders). Reanimated corpses are hard to kill.

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