Visited links sometimes don't change color, sometimes do, at the same sites.

Question

I am using Firefox 4.0.1 under Win XP. Under Options/Content/Colors, the color of unvisited links are blue and visited links are purple. However, when I visit a link by clicking on it, the link temporarily changes color but after I visit the link and return to the original page, "'''''sometimes'''''" the link has reverted to its original blue (the unvisited color), and "'''''sometimes'''''" the color becomes the color it should be -- purple for a visited link. Using IE, the color always changes as it should.

Answer 1

Thanks for the input.  I tried that, and it didn't work.  It appears to work for everything else - just not download links. 
Here's an example of my links:
<a href="http://cdn.setxvideo.com/001.MTS" target="new">001.MTS</a>
in my header is
<style type="text/css">
a:link {background-color:#B2FF99;}    /* unvisited link */
a:visited {
background-color:#FFFF85;} /* visited link */
a:hover {background-color:#FF704D;}   /* mouse over link */
a:active {background-color:#FF704D;}  /* selected link */
</style>
Again, they work correctly in FireFox but not Safari.