Last month, the Virginia Supreme Court ended more than five years of legal haranguing and appeals by ruling that Arlington County had improperly jacked up a 1980 property assessment on a building in Crystal City from $11.35 million to nearly $15.5 million.

On the surface, the case appeared to be a cut-and-dried local issue involving only building owner Albert Ginsberg, on the one hand, and embarrassed Arlington County officials, on the other.

But there was a little twist beneath the surface that made the case more interesting: The primary tenant in Crystal City's Martin Van Buren building at 2511 Jefferson Davis Hwy. is the federal government.

Since 1970, the General Services Administration has leased most of the building for use by the Navy. And under terms of a clause in that 135-page lease, the goverment is liable for the share of taxes paid by the building owner to the county equal to the percentage of space it occupies in the building. When GSA leased the building, that number was 63 percent; it is now 89 percent.

So, for parts of the last two weeks, GSA property managers and lawyers have been trying to figure out just who owes who how much money.

It works like this: Since Ginsberg had been paying his property taxes promptly to Arlington at an unfair rate, he is due a rebate -- according to the court's opinion. And, if Ginsberg had been asking the government to pay its share of the increased taxes -- as allowed by the lease -- he now would owe GSA a similar rebate.

Now the fun part: Ginsberg, for more than five years, has never asked the government to pay the increased taxes, according to James G. Whitlock, GSA's regional public buildings commissioner.

According to the Supreme Court opinion, Ginsberg testified in lower courts that the fair market value of the property was about $10 million and matched his December 1979 purchase price. He said he expected to receive a 6 to 8 percent return on his investment "and considerably more than that after expiration of the existing lease" in 1990, according to the court papers.

"He is somewhat of a hero, I guess, because he knocked down the tax rate that we should be paying," Whitlock said. "He's no dummy, he's eventually going to come in and ask us to pay the back taxes that we owe, however."

Ironically, GSA officials -- including Whitlock -- have labeled Ginsberg as one of the federal government's worst landlords, accusing him of often failing to meet contractual terms unless pressured. Ginsberg is the owner of a building in Silver Spring that suffered a major fire in 1983, destroying several floors of the National Weather Service headquarters. The fire allegedly was spread by flammable ceiling tiles that were supposed to have been removed months before by Ginsberg's crew.

But Whitlock said that in this case, Ginsberg went out of his way to spend his own money to challenge the assessment.

"If we would have known about the assessment, we would have paid the legal costs of the challenge," Whitlock said.

Meanwhile, GSA has set aside about $500,000 to pay increased taxes and other escalator clauses in the contract that Ginsberg has not asked the government to pay since he bought the building -- and the government contract that was first signed in 1970. "We have probably accrued more money than we've needed," Whitlock said. "We'll owe him something, but his challenge probably saved the federal government about $200,000."

A spokeswoman for Ginsberg's New York-based Plaza Realty Investors, which manages his Washington properties, said he was out of town and unavailable for comment. She refused to put a reporter in contact with other company officials.

William F. Sullivan, 38, has been named commissioner of the Public Buildings Service at the General Services Administration, succeeding Lester L. Mitchell, who resigned earlier this month. Sullivan, who came to Washington with the Reagan administration in 1981, is now associate deputy administrator for logistics at the Veterans Administration.

This week, Sullivan said he is looking to bring "quality service" to GSA customers and "stability" to the creative programs that GSA is administering.

"It's way too early to talk about changes," he said. "I want to take a long, hard look at the people and what they do and see how they are being used."

Sullivan plans to bring with him to GSA two career staffers: Timothy J. Ganous, a special assistant of his at the VA, will take on similar undefined chores at GSA, and Melanie Walls, his secretary, also will transfer to GSA.

"One thing I do not plan to do is build a big inner staff that will in any way duplicate the functions of the people who are already there," Sullivan said. "I want easy, open access. I want the people around me to feel free to offer ideas."

GSA is inviting potential bidders to inspect the Blair House complex on Pennsylvania Avenue at 10 Thursday morning as a $6 million to $8 million reconstruction project gets under way. Under orders from the State Department, which uses the historic complex to house foreign heads of state, GSA is installing a new master bedroom suite on the back side of the building and making major fire and safety improvements.

The U.S. World's Fair pavilion in Knoxville, Tenn., soon may become home to a World War II museum commemorating the exploits of Tennesseans. GSA, following guidelines from the Commerce Department, built the $12.4 million wedge-shaped structure for the fair; it had no usefulness as an office building after the event. Eventually, the property was turned over to the Education Department and given to the city for use as an educational facility.

George P. Cordes, GSA's regional administrator in Philadelphia, has assumed the duties of deputy associate administrator in Washington. He is temporarily replacing Robert J. DiLuchio, who is serving as acting commissioner of public buildings. DiLuchio will remain with Sullivan, and GSA officials said they expect him to be considered for the permanent job as deputy there.