Erin and Scott Mirsky had been waiting for days. As darkness settled over their Potomac cul-de-sac, they lit up their two-story ranch house like an all-night diner.

A Comcast technician was supposed to arrive between 5 and 8 p.m. It was after 10. The Mirskys' lights beckoned: This is the house. We're awake. Please don't go away without restoring our Internet access.

As the hour neared 11, Erin called Comcast customer service -- the last of several such calls she made that evening last month. The representative, she recalled, told her that the technician had "just" tried to call them and could not get through. "That is a lie," she replied. He asked how she could know such a thing, because he'd had her on hold for quite a while.

A management consultant who has a graduate degree in telecommunications, Erin fumed. The Mirskys live comfortably, with twin baby boys, two jobs and two cars, but the frustrations of the technological life can raise the blood pressure.

Because she has caller ID and call waiting, she informed him, and because she's not an idiot. The representative apologized. If the Mirskys would agree to reschedule, he would make sure a technician would come to their home first thing the next day.

Irritated but still hopeful, the Mirskys went to bed. The next morning, after two weeks of sporadic outages in their $540-a-year high-speed Internet service, Scott would be told that no technician was scheduled to visit.

Some Comcast customers in Montgomery County say the company is pushing them beyond the limits of consumer endurance. But Comcast says a rival, Verizon, has cut hundreds of Comcast lines in Montgomery and caused thousands of service disruptions in its haste to create infrastructure to compete in providing high-speed Internet access and other services.

Comcast calls itself the nation's leading provider of cable services, with 21.5 million subscribers in the District, Maryland, Virginia and 33 other states.

Telecommunications giant Verizon rolled out its fiber-optic, "to the premises" service in Montgomery this year and is expanding to other parts of Maryland. It also is launching the network in Virginia and a dozen other states. Verizon spokeswoman Christy Reap conceded that "it's been impossible . . . to pursue a construction project of this magnitude without hitting lines and causing accidental damage to other people's utilities."

Complaints on the Increase

County officials say that last month, 265 residents filed complaints about Comcast with Montgomery's office of cable and communication services, up from a monthly average of about 100 since the beginning of the year. Comcast serves more than 220,000 subscribers in Montgomery.

Officials in Anne Arundel and Prince George's counties do not report increases in complaints about Comcast, but company spokesman Jim Gordon warns that service disruptions might occur there, as well.

"The 'build out' has been more robust and more active in Montgomery than in the other two jurisdictions, but it's ramping up," Gordon said.

Comcast wrote Montgomery County Executive Douglas M. Duncan (D) in late June, asking the county to "order Verizon to stop work until the County is able to evaluate the situation." Duncan made no direct reply, but on Thursday, a county official wrote the state's Public Service Commission, requesting an investigation of "Verizon's practices."

"It's not at all surprising that we're hearing from the incumbent that they are suffering as a new kid on the block is attempting to roll out a service," Jerry Pasternak, a Duncan aide who handles cable matters, said of the Comcast letter.

Christine E. Nizer, a spokeswoman for the Public Service Commission, said: "There are times when lines do get struck. That's just a reality of digging."

Gordon could not say whether the Mirskys' troubles were caused by Verizon, but he conceded that a Comcast contractor incorrectly diagnosed their problem, resulting in a canceled technician visit. "We certainly apologize for any inconvenience this may have caused the customer," he said.

High-Speed Frustration

The Mirskys said that they first noticed trouble with their Internet access June 11 and that they waited until June 17 to call Comcast. A technician was scheduled to visit June 23, according to Erin's log of her recent dealings with the company.

On June 20, a Comcast representative called to say that the problem had been fixed and that their service appointment had been canceled. Scott told the company representative that their access was still spotty, he said, and he requested that the technician come as planned on the 23rd.

That night, they lit their house brightly and waited. After the technician failed to show the next day, Scott went to a Comcast office to pick up a new modem.

The couple spent several hours on the evening of June 24 installing the modem and talking to Comcast technical-support personnel. The couple and Comcast personnel tried to work through the complexities of firewalls and the couple's wireless router. Whatever the reason, the new modem and the tech-support-assisted tinkering failed to restore their Internet access.

Comcast did agree to credit their account $40 for the two missed appointments and $45 for the cost of a month's Internet access, which the Mirskys purchase as part of a bundle that includes television service.

A Comcast tech-support worker told Erin, she recalled, that the problem was with the couple's Dell computer. She was eager to have her Internet access restored that evening to allow her to work from home that weekend and save a trip to her office in Tysons Corner. The suggestion that the problem was not Comcast's infuriated her.

"Listen," she recalled telling the Comcast worker, "if you transfer me to Dell, my next call will be to cancel this service."

In the end, she didn't cancel. But she did drive to Virginia that Sunday to check her e-mail and do some work at the office.

Four days later, without a single actual visit by a Comcast technician, the Mirskys' Internet access was restored -- seemingly by itself. "It's alive," Erin joked.

The final frustration occurred last week, when Comcast's bill arrived. The Mirskys' anticipated $85 in credits did not appear on the statement -- only $45 worth. And there was a charge of $65.94 listed as an "online adjustment."

Erin got back on the phone. The Comcast representative heard her out, she said, and then said: "Uh-oh." He put her on hold while he did what he called "some magic." When he got back on the line, he said he had turned the "online adjustment" into a credit.

Erin is waiting to see what appears on the August bill.

"I really like the service," Erin said of the technology that Comcast provides. "But when it goes down, it turns into a fiasco. Anytime you have to call them, it's a runaround."