The strange new version of "The Prisoner of Zenda" opening today at area theaters aspires to be a comic travesty on Anthony Hope's durable, rousing adventure story. But the liberties it takes are seldom justified.

For example, eliminating the dashing, intrepid hero, Rudolf Rassendyll, eliminates the delightful genetic joke that rationalized the plot to begin with. Rassendyll could pretend to be the king of mythical Ruritania only because he and the newly crowned monarch-who is abducted by a usurper-were in fact kinsmen.

Three generations earlier a King Rudolf of Ruritania had had a notorious affair with a Rassendyll lady that resulted in a fatal duel and a long-nosed, red-haired offspring who was the spitting image of the king.

Since that scandal, the male progeny of the Rassendylls would display a curious Ruritanian taint every so often. Rudolf, a foreigner but an inheritor of the telltale resemblance, finds himself in a unique position to aid the unfortunate king (another Rudolf) while on holiday in the politically volatile Ruritania.

The most famous and satisfying of the straightforward film versions is John Cromwell's 1937 production with Ronald Colman. The lamentable spoof now before us was conceived as a starring vehicle for Peter Sellers, who plays three role with no vitality; the expiring old king; the new king, a twit with a lisp; and a look-alike British cabbie who is recruited for unlikely heroic imposture by the king's desperate advisors, played by Lionel Jeffries and Simon Williams.

Offhand, I can't recall another comedy with an energy level as disastrously low as the one retarding "The Prisoner of Zenda." Although the finale generates a little slapstick turbulence, the movie looks and feels inert for the longest time. It's difficult to decide where to pin the blame. Cinematographer Arthur Ibbetson is usually a guarantee of something static. But it's also conceivable that director Richard Quine, who supervised some of the more entertaining comedies of the 50's (notably the wonderful "Operation Mad Ball"), has long since run out of gas.

Moreover, writers Dick Clement and Ian La Frenais neglected to invent a funny version of the original story.

Incredibly, the heroic attributes once possessed by Rudolf Rassendyll are now monopolized by the erstwhile unregenerate villian Rupert Hentzau, who even switches sides to give the good guys an indomitable swordsman at the climax.

The only lively and amusing performers in sight are Stuart Wilson, a young English stage actor who makes Rupert an irresistibly high-spirited, mocking, cad, and Gregory Sierra, who demonstrates unexpected farcical talents as an insanely jealous nobleman. But Sellers appears to think that giving the king a lisp and the cabbie a Cockney dialect will carry the show. On the contrary, they help to put it into a deep coma.