Earnings for Computer Network Corp. were reported incorrectly in Tuesday's Business section. In last year's second quarter, ending Sept. 30, the company lost $545,000 (28 cents a share). Third-quarter profits the previous year were $64,000 (3 cents).

Computer Network Corp. reported a profit of $103,000 (4 cents a share) on revenue of $7.9 million for its third quarter ended Dec. 31, 1984.

The D.C. computer-service company -- which is under new management as a result of a bitter shareholder fight 18 months ago -- hailed the profit as the beginning of a turnaround. Comnet posted a loss of $545 million (28 cents) during the previous quarter.

However, it was unclear how the company's third-quarter earnings compared with the same time period a year ago when it earned $68 million (3 cents), on revenue of $3.5 million, because those earnings were not restated to reflect the acquisition of Ford Laboratories Divisions.

Comnet President Robert Bowen said that if the Ford Lab revenue were subtracted from this year's earnings -- and the interest income that the company would have received from the cash it used to by the company -- Comnet "would have been profitable still" during the most recent quarter.

Comnet reported a nine-month loss of $968,000 (48 cents) on revenue of $14 million, compared with a year-ago loss of $916,000 (49 cents) on revenue of $11.5 million.

* Black & Decker Corp. reported profits of $29 million (57 cents a share) for the first quarter of its fiscal year, up 9 percent from $26.7 million (56 cents) in the same period of the previous year.

The Maryland-based tool and appliance company said first-quarter sales increased to $503 million this year, from $358.1 million in 1983.

* Universal Security Instruments Inc. reported earnings of $70,052 (2 cents) for its third quarter ended Dec. 31, compared with a loss of $396,989 (10 cents) for the year-previous period. Sales in 1984 rose to $3.5 million from $2 million.

For the nine months ended Dec. 31, the Owings Mills, Md., company posted a loss of $834,148 (22 cents), compared with a loss of $557,988 (18 cents) the year before. Sales increased to $8.4 million from $7.3 million.

Universal Security, produces video products, telephones and security devices.

* Ryland Group Inc. of Columbia reported 1984 profits $9.4 million ($1.52), a 40 percent drop from earnings of $15.7 million in 1983. Sales increased to $404.2 million from $394.5 million the year before.

For the fourth quarter, the home-construction company reported net earnings of $2.5 million (39 cents), down 31 percent from $3.6 million (58 cents).