Image distortion in some PCs

In a couple of machines we are having an image distortion problem
which we cannot replicate in other machines.

On the side menu bar we have text images which are links and which have an
‘on hover’ effect. On hovering over a link the text image color changes to
orange and we see a help text below. The help text is also an image. That is
how it should work normally.

But in the abnormal machines, when we move from one link to the link below
and we are in the area between the 2 links, wesuddenly see the first link
duplicated below all the links and the help text image completely distorted.