This is really very strange. I cannot see any reason at all why those three categories should not work when the rest do. They are even interspersed in the stylesheet, so there could not be an error that cuts off the end from processing.

Since you are not using hover features, it would be simpler for you to make the images foreground instead of background images. Rename or copy catbg67.png to catimg67.png and see if that is picked up. The stylesheet rules would then become redundant except for a general rule that top categories are 102px high.