Roy Wright toiled for the Maryland Highway Administration for five years until a stroke forced him to retire early in 1975. His two-year wait for disability benefits paid off handsomely; the first monthly check was a lump sum of more than $3,000.

The next month Wright got another check for $3,336.51, about 23 times as much as the $145 a month he should have received.

The large payments continued month after month after month, for so long, a state official said yesterday, that Wright has been overpaid by almost half a million dollars in the last eight years.

And now, the state wants the money back, all $446,102.02 of it.

"This kind of situation is damned embarrassing," said Bennett Shaver, executive director of the Retirement and Pension Systems, who likened the computer foul-up to "an administrator's nightmare."

State auditors uncovered the goof last month, Shaver said. Instead of monthly checks of $249, Wright's monthly disability benefits were $5,957.

Attempts to contact Wright failed, Shaver said, so the state filed suit against him on Oct. 3 in Baltimore Circuit Court.

Judge Joseph H.H. Kaplan ordered the 58-year-old man's assets frozen, including accounts at Union Trust Bank, First National Bank of Maryland and Provident Bank of Maryland.

Wright, who lives in the 2500 block of Lodge Farm Road in Edgemere, Md., could not be reached yesterday for comment. His attorney, Ralph Rothwell of Baltimore, said he hasn't worked out a repayment plan. He wouldn't comment further.

Shaver said the overpayments happened under the agency's old computer system.

Under that system, the first check issued was to include back payments and the disbursement figure then would be purged from the system. A new, lower monthly payment was supposed to have been entered in the computer system after the purge. In Wright's case, after the first check for $3,336.51, a new monthly payment of about $145 should have been entered in the agency's computer.

But it wasn't.

"In this case the system failed," Shaver said. "We understand how but not why. We don't have a piece of paper that says Mary Ann Smith punched up the wrong card."

Shaver said that the investigation in his office on the case has been closed and found no evidence that anyone in his agency, which employs about 80 persons, had worked to get extra money for Wright.

"If you were earning $30,000 a year and after a few years of retirement you've got $230,000," said Shaver, "you would know something is wrong."