Thumnails don't work on Firefox

I have embded my flash using SWFObject method but it did not solve the problem.
My link to my site where problem occured:
Procceed by clicking name “Polski-wejscie” (english version doesn’t work yet) next Architektura and finally one of two texts - links (both have the same problem).
On IE everythig works fine but in Firefox or Safari thumbnails are not showed at all.

When I loaded my site locally (using file on hard disk) suddenly every thumbnail is loaded properly even in Firefox but when I just want do it from server every thumnail disapeares…

What is going on??