"Among his souvenirs [in 1977] were an Open Era winning streak record of 46 matches and the French and U.S. titles. His streak, begun after Wimbledon, was stopped at Aix-en-Provence in September by Ilie Nastase, who used one of the controversial "spaghetti" rackets that produced weird strokes and bounces. Vilas quit in disgust; such rackets were shortly banned."
Because Nastase's "spaghetti" racquet (leave it to Nasty to utilize such trash) was shortly thereafter banned as illegal, I believe that the record books should be re-written to ignore this loss.
If you leave out the Nastase match (at Aix en Provence, France; 26 September), then Vilas won 73 matches in a row before losing in a Round Robin walkover to Eddie Dibbs at the Masters in NYC in January 1978.