In the last month I have started to get the same problem. It's not the filter, I've checked that because I did have that happen when I didn't turn off the screen before putting the GPS in my pocket!! I've tried to load using base camp and by direct copying to both the card and the unit ( I have an Oregon 650). It worked fine until recently . It's driving me mad. If I check it on base camp it looks fine but once out in the field - in tHis case 3000ft up a mountain - no caches. Thank goodness for my iPhone!!
Any ideas anyone?