UNC Resources' profits were trimmed sharply in the third fiscal quarter ended Dec. 31, because of "difficulties" in uranium operations, the Falls Church company announced.

The parent company of United Nuclear Corp., largest independent uranium producer in the U.S., UNC said earnings were down to $122,000 (1 cent a share) compared with $9.4 million (87 cents) a year earlier although revenues edged up to $72.8 million from $71.8 million.

Uranium production was "severely curtailed" by delays in receiving approval to restart a mill in New Mexico that was closed July 16 and not back in business until November following a spill.

Other factors cited by UNC were higher mining costs and expenses of the environmental cleanup. Insurance claims are being filed to recover costs and loss of profits but have not been reflected in the corporate earnings data.

UNC also had continuing losses at a subsidiary in Florida that recovers uranium from phosphoric acid but which recently suspended operations. UNC has filed a federal lawsuit seeking damages from the W. R. Grace & Co., which operates an adjacent plant. The Falls Church firm noted that it is carrying the Florida investment on its books at $40 million "which may require reevaluation if the situation cannot be resolved satisfactorily."

For the nine months ended Dec. 31, UNC profits were $7 million (65 cents) vs. $26.5 million ($2.52) as sales declined to $208 million from $211 million.

Seperately, a federal judge in San Diego cleared the way for arbitration of a five-year-old uranium supply dispute between UNC and General Atomic Co. But the issue remains tangled because a New Mexico state judge already has ruled against General Atomic. UNC is claiming $2.3 million in damages.

Solon Automated Services, Inc., a Washington-based supplier of laundry equipment services for multifamily housing and owner of the Sugarbush ski resort in Vermont, said earnings were flat in the fourth quarter ended Sept. 30, at $1.44 million (40 cents a share) in both periods, although sales rose to $16.5 million from $14.5 million.

For the full fiscal year, Solon earnings rose modestly to $5.3 million ($1.87) from $5 million ($1.75) as sales jumped to $66.4 million from $57.7 million.

Student Loan Marketing Association, created by Congress in 1972 to provide a secondary market for guaranteed college student loans, reported 1979 earnings of $6.3 million ($38.08 a share) compared with $5.9 million ($35.43) a year ago. Earning assets -- mainly loans purchases and advances to lenders -- soared 61 percent to $1.5 billion.

Edward Fox, president of the business named Sallie Mae, said the growth last year reflected an ability to meet rapidly growing needs of lenders at a time of sharp increases in student loan demands, high interest rates and tight money.

Greater Washington Investor Inc., a small business investment firm, suffered a net investment loss of $295,874 in 1979 which was more than offset by capital gains from securities transactions and appreciation of investments. As a result, net operating assets increased to $871,394 (68 cents a share).

After selling 696,000 new shares that brought in $621,880. GWI's year-end net asset value was $2.8 million (1.56 a share), a 30 percent increase in per share value even after dilution for more shares outstanding.

Macke Co., a food services and vending firm based in Cheverly, reported that profits declined to $985,000 (32 cents a share) in the first fiscal quarter ended Dec. 31 compared with $1.4 million (45 cents) a year earlier, reflecting what the firm said were "disappointing results" in restaurant operations. Sales rose to $68.8 million for $62.9 million.

Ryland Group, a house building company based in Columbia, reported profits in 1979 rose to $7.9 million ($2.48 a share) from $6.3 million ($1.91) a year earlier. Sales contracts signed last year rose 6 percent to 3,764, with a dollar volume of $252 million, up to 19 percent.