CMS Made Simple Forums

I finished the site and customer noticed quite unusual problem - when he tries to view page via "Preview" facility in Administration panel (Content->Pages), it gives
where login panel should be. Frontend is working absolutely fine, just "Preview" Facility in the backend is failing Any ideas how to fix it?

What ver.?...

If newer ver. of CMSMS the preview tab doesn't work should have been removed now there is a preview link next to submit, cancel, apply buttons, try that...

Preview never did work that good especially if you had more than one content block...