PAX USE OF A LAPTOP COMPUTER CAUSED CAPT'S COMPASS TO PRECESS ABOUT 10 DEGS.

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IN CRUISE FLT AT FL310 25 NM W OF THE DFW VOR; THE #1 COMPASS SUDDENLY PRECESSED 10 DEGS TO THE R. I ASKED THE FIRST FLT ATTENDANT IF ANY PAX OPERATED ELECTRONIC DEVICES WERE IN OP IN THE CABIN. SHE SAID THAT A PAX IN SEAT X HAD JUST TURNED ON HIS LAPTOP COMPUTER. I ASKED THAT THE PAX TURN OFF HIS LAPTOP COMPUTER FOR A PERIOD OF 10 MINS; WHICH HE DID. I SLAVED THE #1 COMPASS; AND IT RETURNED TO NORMAL OP FOR THE 10 MIN PERIOD. I THEN ASKED THAT THE PAX TURN ON HIS COMPUTER ONCE AGAIN. THE #1 COMPASS IMMEDIATELY PRECESSED 8 DEGS TO THE R. THE COMPUTER WAS THEN TURNED OFF FOR A 30 MIN PERIOD DURING WHICH THE #1 COMPASS OP WAS VERIFIED AS NORMAL. IT WAS VERY EVIDENT TO ALL ON THE FLT DECK THAT THE LAPTOP COMPUTER OP WAS ADVERSELY AFFECTING THE OP OF THE #1 COMPASS. I BELIEVE THAT THE OP OF ALL PAX OPERATED ELECTRONIC DEVICES SHOULD BE PROHIBITED ON AIRLINES UNTIL THE SAFE OP OF ALL OF THESE DEVICES CAN BE VERIFIED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR REITERATED THE INCIDENT AND ADDED THAT HE HAS SENT IN ANOTHER RPT ON A SIMILAR INCIDENT. HE IS A SAFETY COMMITTEE MEMBER AND CLAIMS THAT MANY CASES HAVE BEEN RPTED AND THAT HE IS CONVINCED THAT MANY LAPTOP COMPUTERS DO AFFECT HDG AND NAV INSTS. HE IS EXTREMELY CONCERNED WITH THE POSSIBLE FUTURE AFFECTS ON FLY-BY-WIRE ACFT. COMPUTER WAS AN IMPORTED PC CLONE.