When I visit your site with the Firebug plugin enabled in Firefox it shows a script error from the amazon script. It appears they are using a very old customized version of JQuery and it is not compatible with the newer version of jquery that is also included in the page by mojoPortal.
I was able to produce the same problem on www.joeaudette.com but I then removed it.
Doing some searching on it I found this post which seems to confirm it
It just seems like amazon has done a very lame job in implementing this. Even when I use Chrome browser on the amazon site when I create an image link it says mouse over it to see a preview but when I mouse over it it flashes an empty box briefly that disappears right away, and this is right on the amazon site. I would have thought a company like amazon would do a better job with their affiliate implementation, but my verdict is they have not got it right and have done half hearted implementation and not enough testing.
Sorry but I don't have a solution for this at the moment.