James Joyce's "Ulysses," a landmark of 20th century literature, has a reputation for obscurity that has scared off several generations of students. But at least some of that obscurity may be the result of thousands of typographical errors made in 1922 when the novel was set into type in Paris by French printers who knew no English, according to two scholars. "The book is a proofreader's nightmare, says Johns Hopkins University English professor Hugh Kenner. "Errors settle like sludge to the bottom, and the current editions incorporate most of them." Kenner estimates about 6,000 errors, including transposed words, missing phrases and missing or misplaced commas, in the current edition. Some of the errors stem from Joyce's method of scribbling extensive changes -- nearly a third of the present text -- on the margins of page proofs; the errors were compounded by the author's eye problems, which eventually made it impossible for him to read the proofs. Still more errors crept in through pirated editions. Kenner is helping a colleague, Hans Gabler, correct all these errors. For three years, Gabler has been feeding more than a million words from early manuscripts of "Ulysses" into a computer in West Germany. He hopes to publish a definitive text in 1983.