No, no errors at all, the upgrade worked like a charm. That's why this is weird.
One thing, I have noticed JQuery is not available anymore directly by Kentico. I have to check if I was using some JQuery transformation to shown the images, and if so, I have to add a reference to a new JQuery file myself.
I'll try again tonight.
Thanks
Vilém, GetImage is a method used as follows:
GetImage(object attachmentGuidColumn)
<%# GetImage("ABC") %> --•Returns complete HTML code of the image whose GUID is stored in the column of the given name.
Thanks a lot !