I've had this problem as well. Neither of these above responses help me because I have no "all items" available to check.
Normally, there are two infinitely long lines following the cursor, one is vertical and one is horizontal, and I have a completely white background, and I normally can easily see these two lines without any issues. I cant remember what color it is, (black or dark pink) but randomly, they "almost" disappear, and I say "almost" because I can faintly see them if I squint, but its as if they are one shade above white which is practically invisible.
So, my question is the same, why do they almost completely disappear, and how can we get them back?