A road by any other name would not sound so sweet. So when the U.S. Postal Service tried to rename a particularly posh strip of Fifth Avenue, residents of Manhattan's Upper East Side complained.

Loudly. And, as it turns out, successfully.The leader was Marcy Pedas Sigler, who had lived on Fifth Avenue since 1973 - until she opened her mail last week and discovered her once-tony address had been changed to a pedestrian "1080 Museum Mile."

"The last cab driver I had couldn't find Lincoln Center," Sigler complained Tuesday. "Can you imagine trying to find 1080 Museum Mile?"

Well, no. But the folks at the post office obviously could.

"Dear Postal Customer," began the address-switching card sent to people living from 82nd Street to 104th Street, "to ensure accurate and timely delivery, it is very important to make sure all the mail sent to you displays the EXACT address as it appears here."

The city started using the name Museum Mile for the 22-block stretch in 1981. There are 10 museums on Museum Mile - and all use a Fifth Avenue address.

While the city frequently provides street aliases - Fashion Avenue for Seventh Avenue, Avenue of the Americas for Sixth Avenue - people move to Fifth Avenue for a reason.

It's known internationally, easily identifiable to folks from Tennessee to Tokyo. And the location - opposite Central Park, amid the museums - makes it one of the city's most desirable addresses.

Jacqueline Onassis' Fifth Avenue apartment at East 85th Street is reportedly on the market for $9 million. Would an address of 1040 Museum Mile sound as good - or sell for as much?

One Sigler neighbor, Dr. Brian Coan, was bemused by the notice of a new address. "I always thought the purpose of an address is so you can FIND stuff," he joked.

But others weren't laughing. Sigler, the head of her building co-op board, received nine calls from angry tenants. Coan had problems getting his mother's pension check because of the changing addresses. Doctors, businesses and residents began computing the cost of new business cards and stationery.

When they finished the math, it added up to some angry people. The post office said Wednesday it had moved to defuse the controversy by allowing residents to use either address.