PLT OF BE20 IS DISTRESSED TO LEARN THAT HIS GARMIN 530 GPS SYS MAP DISPLAY LOCKS UP IN THE VICINITY OF P-40. UNABLE TO DUPLICATE IN SUBSEQUENT TESTS OUTSIDE OF THE VICINITY OF THE PROHIBITED AREA.

Narrative

I WAS ON AN IFR FLT PLAN FROM SUSSEX COUNTY ARPT; DE; GED TO HGR. PART OF THE ROUTING CLRNC WAS TAKING THE 321 DEG RADIAL FROM EMI AND THEN INTERCEPTING THE 089 DEG RADIAL INBOUND TO HGR. I WAS USING A GARMIN 530 GPS TO NAV WITH; WHICH IS AN IFR CERTIFIED SYS AND HAD A CURRENT GPS DATABASE CARD. BASICALLY; THE ROUTING ATC HAD GIVEN ME WAS TO TAKE ME AROUND P-40 (CAMP DAVID). SOMEWHERE E OF P-40 AND FLYING WBOUND; POTOMAC ADVISED THAT I SHOULD TURN IMMEDIATELY 40 DEGS R TO AVOID P-40 CAMP DAVID. I CHKED THE GPS DISPLAY AND THE MOVING MAP SHOWED ME ON A TRACK THAT WOULD CLR P-40 TO THE N. HOWEVER; I DECIDED TO TAKE ATC'S ADVICE AND TURN 40 DEGS R. IT WAS THEN THAT I NOTICED THAT THE MOVING MAP IMAGE WAS FROZEN -- THE ACFT DID NOT CHANGE POS ON THE MAP. AT THAT TIME I WAS USING THE OBS (OR HOLD) FEATURE ON THE GARMIN 530. WHEN I SWITCHED TO THE AUTOMATIC SEQUENCE MODE; THEN THE MAP INDEED READ CORRECTLY AGAIN. AFTER SOME TROUBLESHOOTING; I FOUND THAT THE GARMIN 530 DISPLAY WOULD 'FREEZE' WHENEVER I USED THE OBS FEATURE; BUT WOULD READ OK ON THE AUTO-SEQUENCE. APPARENTLY THERE SEEMS TO BE SOME SORT OF SOFTWARE GLITCH. ALTHOUGH THERE WAS NO VIOLATION ON PENETRATING P-40; MY GPS HAD A MALFUNCTION WHICH WOULD HAVE LED ME INTO A PROB. THANKFULLY; POTOMAC ATC ADVISED ME IN TIME AND A VIOLATION WAS AVOIDED. I THOUGHT IT WOULD BE A GOOD IDEA TO MAKE A RPT IN CASE THERE ARE OTHER USERS WHO MAY COME ACROSS THE SAME PROB. I'VE MADE CONTACT WITH GARMIN AND EXPLAINED THE ERROR SIT. THIS PARTICULAR GLITCH IS A PUZZLEMENT TO THEM AS WELL. THEY SUGGESTED THAT THERE MAY BE SOME TYPE OF GPS SCRAMBLING OR JAMMING GOING ON WITH THE SIGNALS IN SENSITIVE AREAS LIKE P-40. GARMIN SAID THAT MANY OF THE GPS COMPLAINTS LIKE MINE SEEM TO COME FROM THE WASHINGTON; DC AREA (LANGLEY AFB; TOO). SHORTLY AFTER MY INCIDENT I CONTINUED TO EXPERIMENT WITH THE GPS IN ALL DIFFERENT MODES AND IT WORKED 100%; ALL THE TIME. SO; DID THIS 'ANOMALY' GO AWAY; OR IS THERE SOME TYPE OF SIGNAL SCRAMBLING GOING ON NEAR P-40/CAMP DAVID?