I've tried using version 6.1.3.3000, 6.2.600.0, some versions of maxthon 5, maxthon 5 and 6 portable, my phone (android) and a different computer with maxthon 5.   I'm not sure if this is a known issue that simply hasn't been fixed or if there is some way in.   In every case I've had the same problem, I log into uu.me (sometimes it takes a few tries) and can access Maxnote and UUMail.  When I click on passkeeper I get a screen asking for me to enter my Maxthon Account Password, when I