I have the same problem
Lytebox  works ok, it occasionally causes a problem in firefox
lyebox based on moo cause a black screen to fill half the screen
slimbox creates the thumbnail but when it is clciked it simply launches a new page with the image
Grey box the same
thickbox works but does not make the clicked image fullsize

Could anybody offer any suggestions, do I need to any any code to the index file?

thanks