I have been having the same problem, and have not found any answers online.
My work around was changing the margin size to narrow, and all the borders seemed to show up in print preview. I then set it to the custom margin setting with .375" on the sides, and the borders were still there, although any bigger of a margin and the borders seemed to disappear again.
When the borders disappear, you can get them back by changing the column width, by even .001" and the border will reappear in the print preview, although that may cause a border somewhere else to disappear.