rocknbil - 10:36 pm on Mar 29, 2010 (gmt 0)
Pages will float up and down over time before settling in to where they will more or less stay. A site redesign often suffers a temporary loss but if the page's changes are improvements, it will come back. Unless you just happened to catch it on the day you were indexed, I hardly think this would be the cause.
Also you probably didn't note what competing pages were "above you" on previous days. 5 or 10 competitors could have entered the serps, or maybe those competitors also could have changed their content. It could be a lot of things.
I can't imagine that changing from image based links to text links could be anything but positive, wait it out, see what happens.