ALTDEV ALT OVERSHOOT.

Narrative

I WAS DEPARTING A NON-TWRED FIELD IFR (OLV) FLYING A BEECH 85 BONANZA. NO PAX. I HAD ALREADY RECEIVED AN IFR CLRNC FROM MEM CLRNC DELIVERY; AND DOUBLE CHKED ALL INSTRUCTIONS AND INSTS. THE CEILING WAS AROUND 900 FT AGL; TOPS AT 7200 FT MSL. I HAD BEEN CLRED TO 2000 FT; EXPECT 8000 FT IN 10 MIN. AFTER TAKING OFF; BEGAN A NORMAL CLB; AND CONTACTED MEM APCH. AFTER ENTERING THE CLOUDS; I NOTICED THAT MY ATTITUDE INDICATOR WAS SHOWING A NOSE DOWN INDICATION. IN ADDITION; MY #1 RADIO (TUNED TO MEM APCH); STARTED CUTTING IN AND OUT WITH A LOT OF STATIC. I WAS DISTR. I GLANCED AT MY AIRSPD INDICATOR WHICH SHOWED MY AIRSPD WAS PROPER FOR CLBING; MY VSI WAS SHOWING 1500-2000 FPM CLB; AND THEN MY ALTIMETER; WHICH TO MY HORROR WAS SHOWING 3300 FT. I RESET MY ATTITUDE INDICATOR AND BEGAN A DSCNT TO 2000 FT. HOWEVER; AS I DID THIS; THE APCH CTLR CALLED AND ASKED WHAT MY ASSIGNED ALT WAS. I TOLD HER 2000 FT AND APOLOGIZED; SAYING I WAS BEGINNING A DSCNT. SHE THEN CLRED ME IMMEDIATELY TO 5000 FT. THE CTLR DIDN'T SAY ANY MORE ABOUT THE ALT BUST; OR IF I HAD CAUSED A CONFLICT. I DIDN'T OFFER AN EXCUSE OR EXPLANATION BECAUSE SHE SEEMED VERY BUSY AND ALSO HAD CLRED ME TO 5000 FT. AFTER ARRIVING IN KNOXVILLE; I BECAME CONCERNED THAT SHE MAY HAVE TO RPT THE ALT BUST BECAUSE OF THE PROX TO CLASS B AIRSPACE.