my altimeter is indicating 400 ft high(560 ft with field elev 150 ft and correct altimeter setting). I got back from a xc trip monday and landed vfr in between rain showers. taxiied in and put airplane up without noticing any altimeter error, although i can't remember actually noticing the altimeter reading. Went back out to airport yesterday and altimeter is incorrect. airplane is hangared, it sat outside for three days while gone, but was indicating correct altitude when i departed for home. i have disconnected static airline to altimeter and it stays the same. also blew out static line. highest altitude coming home was 8000'. airplane has one year and 128 hours on it and up til now altimeter has been ok. anyone have any ideas. thanks fred