CHICAGO — Lori Langer poured herself into her job, putting in extra time calling prospective students as an admissions adviser at American InterConti-nental University Online.

"I would stay an (extra) hour or two a day and come in on Saturday for four to six hours," she recalled. "In order to get my job done, that is what I had to do."

She liked the work and liked the overtime pay, too.

But within a few months, her bosses told her she no longer could get paid for overtime, she said. Tear up your time sheets, they allegedly told her.

While not getting overtime pay did not seem right to Langer, she didn't do anything about it until she was contacted by a lawyer representing some of her colleagues in a federal class-action lawsuit claiming overtime-pay abuses.

With their case churning along in federal district court in Chicago, she and about 175 co-workers have joined what some experts say is the nation's fastest-growing legal battlefront between workers and companies. Since 2000, the number of wage-related cases filed in federal courts has doubled, and most involve overtime claims.

Experts say the increase in overtime lawsuits across the country resulted from a lack of clarity in federal law, which has set rules for overtime wages since 1938.

An update to that law was supposed to clarify eligibility requirements and extend protections to an additional 6 million workers, but many say the revisions only muddied the water and invited litigation.

Traditionally, all workers were eligible for time-and-a-half overtime, except for those in the executive, administrative and professional categories. The 2004 federal changes sought to define more clearly those exempt categories by using new job descriptions such as "exercises discretionary and independent judgment." The change was made because language such as "holds a position of responsibility" was deemed too vague.

But the new descriptions can seem just as fuzzy, while job functions have blurred in an era of corporate downsizing. Clock-punching issues also have become more complicated because of increased travel and flexible schedules.

Tammy McCutchen, a Washington attorney and former administrator of the U.S. Department of Labor's Wage and Hour Division, confirmed that problems persist despite the changes in federal law.

"We tried to change the law and make it clearer. But there are still some uncertainties," McCutchen said.

A major factor is that it has become more difficult to define as overtime the hours someone might work because of individual schedules and time spent out of the office. For example, a saleswoman does not qualify for overtime while she is traveling. But the second she settles down and begins selling using a computer she does qualify, McCutchen said.

Similarly, job descriptions can seem to overlap. A financial adviser who counsels clients cannot get overtime pay, she added. But someone who takes investors' orders can.

FLURRY OF LAWSUITS

These new debates over questions of who is a boss and who is an employee, or when does work begin, have drawn the attention of lawyers to an area of law that largely had been ignored.

At the same time, the government stepped up enforcement of wage laws, leading to a spike in the collection of back wages, which mostly are from overtime-pay cases. In turn, such intervention also has attracted more attention and lawsuits.

Last year, State Farm Mutual Automobile Insurance Co. reached a $135 million settlement with claims adjusters, who said they had not received overtime pay, in violation of California law. Allstate Insurance Co. agreed to pay $120 million in a similar suit last year in California. In both cases, adjusters said they have been wrongly classified as exempt, which cost them overtime pay.

And Cingular Wireless agreed to pay $5 million last year to customer service workers after a government investigation that began at the firm's Springfield, Ill., call center revealed employees were working off the clock before or after their shifts and not being paid for that work. At the time, Cingular denied any wrongdoing and said it had worked with the government to resolve the problem.

'HIGH-TECH SWEATSHOP'

In the case involving Lori Langer and others at American InterContinental University Online, attorney Robin Potter said the company ran afoul of the law when workers were told that they would not be paid for working more than 40 hours.

"Federal and state law says that if you work it, you get it," said Potter, who described American InterContinental's workplace as a "high-tech sweatshop."

"The testimony is that people worked five to 15 hours per week for which they were not paid," Potter said. Workers were told they could only get overtime if they met quotas in recruiting students, she said.

Langer's former employer is a subsidiary of Career Education Corp., based in suburban Hoffman Estates, Ill.

In a written statement, Stuart Chanen, an attorney for the online education company, denied the lawsuit's claims.

The company, he wrote, has paid overtime to hundreds of workers, including those who did not meet their recruitment quotas.

Furthermore, the company conducted its own investigation into the allegations after the lawsuit was filed and "found them to be without merit," Chanen wrote.