With 4.0.4 you have Locus (with apps2sd) at /sdcard/external_sd/Locus. With 4.1.2 it is/storage/extSdCard/Locus. Maybe the problem is here?
Yes, I noticed the change of paths as well. But if that was the problem, it wouldn't work at all, right? But it works correctly for more than a week so... looks like the problem fixed itself?
edit:Oh, well, just now it happened again. After inserting a new point into a category - crash. But then, I saw the point was inserted properly (it was not checked to show on map intially) and everything was working okay. So I checked it (the other points were already checked), gone from points screen back to map and then exited Locus. After starting Locus again, all points from that category were unchecked (points from other categories were left intact).
edit 2:Now I was adding two points using coordinates - the same steps for both. First point was inserted OK, second crashed. Then I renamed the point and it was renamed OK, however, checkboxes of other points got lost. I got up (to list of categories), where I saw 1/49 - that was the number of "checked" points under my category. I entered the category again, chose Select all which checked the checkboxes of all points. Then I got up to list of categories again and there I saw 1/49 - expected 49/49. After opening the category, only the one (freshly added) point was checked.