Joseph L. Pokorney had forgotten about the four parking tickets he received and promptly paid last November. Unfortunately for him the city's computers had not.

So on April 2 when the city towed Pokorney's car for parking in a rush hour zone he found himself facing the $50 towing fine, plus $70 for the four tickets.

Three days later, after arming himself with the canceled checks showing the ticket numbers, Pokorney was assured by Peter Bergin, head of the city's parking ticket collection office, that the tickets would be canceled. Or, rather, that the computer would be told to cancel them.

But three days ago, Pokorney's car vanished again from its Georgetown parking space. The city had hauled it off because the computer still showed the tickets unpaid. (Normally the infamous "Denver boot" immobolizes cars as a penalty for outstanding tickets, but the configuration of the tire on Pokorney's car made "booting" impossible.

John Brophy, head of the city's transportation department's parking division, said unrecorded payments happen "more often" than he would like.

"It happens maybe once a week," he estimated. "And it's an embarrassment."

The problem dates back to November, Bergin said, when the computers at the D.C. Superior Court failed to record an undetermined number of ticket payments. Although transportation took responsibility for ticket payments in October, the court continued to do the actual computer proceeding.

"Mr. Pokorney is one of those that was lost," Bergin explained. Pokorney said he paid all four tickets Nov. 10.

But Joel Lipson, assistant director of the court's data processing system denied that computer problems prevented the payments from being recorded. He said Bergin sent him incorrect information-a charge Bergin denies.

At any rate, on Feb. 20, city transportation took over its own processing and data processing chief, Harry Gray, said yesterday he is still trying to determine how the mistake was made.

He added that he is also investigating a similar case where a second motorist was "booted" twice for tickets he previously paid.

Pokorney calls it a tale of "terminal incompetence."

"It's bad enough to pay twice but to have it happen again three weeks later after I was assured it had been corrected, there's no excuse for that," he said. "It's total incompetence," he said.

Although the city chauffered him to the impoundment lot where his car was towed Monday and again assured him that the problem was solved, Pokorney said yesterday he still fears his auto is unsafe on city streets.

He called the transportation department to check on the tickets. "The operator told me there was a capital A beside the number and she did not know what that meant," he said. Bergin said it means the tickets are paid, but, unfortunately, the computer operator tells the computer what it means, and she didn't know. CAPTION: Picture, Joseph L. Pokorney, standing beside his twice-towed car, shows documents. By Joe Heiberger-The Washington Post