center thickbox in IE8

[Pippo3000]

as many others thickbox works fine for me in Chrome and Firefox but is displaced at the bottom of the page, partially hidden, under IE8 (amazingly enough not all IE8 installations but 1 is enough). Found a topic in the spanish forum which I would like to bring here to the english one for discussion as I have a dummy question:

http://www.prestashop.com/forums/viewthread/18532/discusin_general/problemas_lightbox__thickbox_con_iexplorer_8/

any help is appreciated as any other proposed fix did not work so far.

best
phil