While the cinematic forces of evil, led by the fearsome Darth Vader, went down to interplanetary defeat on a Washington moviehouse screen yesterday, hundreds of would-be patrons lined up outside grumbling that justice and righteousness were not faring very well in the real world.

According to estimates by the management of the K-B Cinema, the theater had oversold Sunday's six showings of "The Empire Strikes Back" by more than 1,000 seats.

Aptly enough, the threat to the galactic serentiy and peace at that corner of the universe located at the 5100 block of Wisconsin Avenue was attributed to a cause that science fiction fans would truly appreciate: a "computer tape drive malfunction."

"This is just a disaster," moaned Ron Goldman, the theater's owner, as hordes of patrons beseeched him for refunds and the theater's line grew to a two-block-long snake of tired, perspiring space fans. He promised to keep on running the film, the second in the Star Wars series, until 3 a.m. if necessary to accommodate everyone.

A spokeswoman for the Capital Ticket Center, which had handled advance ticket sales, confirmed yesterday that a computer "burp" had subtracted hundreds of sales from the list it forwarded to the theater's management. It was that erroneous reporting, she acknowledged, that had led the theater to oversell every show yesterday.

"Whatever it was, it's being repaired and it won't happen again." said Debbie Edwards. "I couldn't really explain what happened unless I took an hour to do it."

Outside in the humid mid-day heat, most of the crowd seemed resigned to waits of up to three hours before they got a glimpse of their mythical heroes. "We just wanted to spend the day with the family anyway," said Brenda Sambuchino of Northwest Washington as her husband and daughter played a game of "21" on the sidewalk. "I'm not really excited about it. It's a holiday anyway, so what the heck."