13
I have installed those modules:
News, NewBB, Mylinks, Who's Online, Xoopspoll, Xoopsmembers, eCal, IpBoard (but inactive for ages), WFSections, XoopsPartners, XoopsHealine.
Most of them are quite out of date, as I had Xoops 2.0.6 updated to 2.4.5 few days ago (but admin panel was working fine in that version). But after 2.5 upgrade I went into xoops_modules table in my database via PHPAdmin and disabled all except System module (set them all as 'isactive=0'). So at the moment only Admin module is active, with blank page still.