More than 100,000 Chesapeake & Potomac Telephone Co. customers might think they've had a summer vacation from telephone bills.

But yesterday the company said the vacation is over: The bills are on the way after a two-month delay.

The customers, most of them in Northern Virginia, have not received bills for local or long-distance service -- or both -- since a computer tape failure in mid-May.

The high-tech roots of the problem were "flaws" in computer tapes that were programmed for preparing the bills, C&P spokesman Web Chamberlin said yesterday. "The program erases itself," he added.

The low-tech solution was to use people to put the billing information into the system, using separate records of the calls, he said.

The result was that many customers did not receive phone bills for serveral months.

An Arlington resident said he had not received a local bill in two months or a long-distance bill in three months. C&P customer service has told him his bill will be mailed Monday.

The customer also said he was told to call C&P if he has any trouble paying the entire bill at once.

"We would be lenient on payment, and would be glad to speak to customers on an individual basis. . . . We're sorry for any inconvenience," Chamberlin said.

The billing delay also involved "a smattering" of customers in Maryland, but was not felt in the District.

The problem also affected an unknown number of bills for long-distance service provided by MCI Communications Corp. C&P, a subsidiary of Bell Atlantic Corp., provides only local service, but sends its bills jointly with those of various long-distance companies. MCI had no comment when contacted yesterday.