I've found where the problem lies!
The stylesheet "/farcry/core/webtop/css/forms.cfm?fsjv=511c" contains nothing! I copied the code it should produce into a CSS file and voila, worked like a charm. Something is wrong, at least for my configuration, but at least now I know where the problem.
Why is this CCS generated using a CFM page? would it be different for every install?