Ultimate Fade uses escalating z-index values. So if your cover is relying upon following the slide show in the page and/or having a higher z-index, either way, at some point it will be overcome by the slide show's escalating z-index. A good solution would be to set the cover's style in a stylesheet on or linked to the page:
Assuming that this is the issue, it would then take 10000 image changes before the problem reappears.
Another solution which is a littler better would be to upgrade to:
Swiss Army Image slideshow
Which can be made to look just like Ultimate Fade, but uses alternating z-index values instead of escalating ones. If you did that, setting:
would be sufficient to prevent the problem regardless of how many image changes there were.