CAPT OF A B737-200 MOMENTARILY LOST CTL OF THE ACFT IN MODERATE TURB DURING HIGH ALT CRUISE DUE TO UNCONTROLLABLE LATERAL ROLLING AND LOSS OF ALT EVEN IN A NOSE UP ATTITUDE. ATC RESPONDED TO THEIR SIT BY TURNING THEM OFF THE AIRWAY UNTIL CTL COULD BE REGAINED; UPON WHICH THEY RETURNED TO ASSIGNED ALT.

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ACFT ENCOUNTERED MODERATE TURB S OF ORF VOR AND WAS SLOWED TO MACH .70 WITH PERMISSION OF ATC. THE ACFT THEN BEGAN DUTCH ROLLING BACK AND FORTH ABOUT 5-10 DEG BANK EITHER SIDE OF LEVEL. AFTER SEVERAL MINS THE ACFT ROLLED HARD R IN A 30 DEG BANK AND IMMEDIATELY ROLLED BACK TO THE L IN A 30 DEG BANK. IN THE PROCESS OF THE FIRST HARD R BANK THE AUTOPLT TRIPPED OFF. WHILE I STRUGGLED TO KEEP LEVEL; THE ACFT DSNDED ABOUT 300-400 FT EVEN THOUGH WE WERE PITCHED NOSE UP WITH ADDITIONAL PWR. I REGAINED CTL WITH PRIORITY TO ATTAINING LEVEL FLT AND I THEN ENCOUNTERED LESS TURB. A CLB BACK TO FL330 WAS INITIATED AND ATC WAS ADVISED AS TO OUR SIT. THE STRANGE PART IS THAT AT NO TIME WAS THE TURB MORE THEN MODERATE; BUT THE ROCKING FORCE WAS EXTREMELY STRONG AND COULD NOT BE OVERCOME. I DON'T KNOW IF IT COULD BE CATEGORIZED AS CLR AIR TURB; I DON'T THINK SO; BUT IT WAS A STRANGE ENCOUNTER. SEVERAL OTHER ACFT EXPERIENCED THE SAME ROLLING TURB; BUT NOT AS SEVERE AS WE DID. SUPPLEMENTAL INFO FROM ACN 391524: RPTED UNABLE TO HOLD TO ALT TO ATC. ATC GAVE US A TURN OFF COURSE AND DSCNT TO LOWER ALT.