I have the same problem. All my discussions with support were not helpful. Complete reinstall of evernote did not work. My login works on the web and all other clients. I am using a macbook air with Mac OS 10.8.2. Evernote is the latest build Version 5.0.6 Beta 2 (400928). I actually haven't installed anything new an my mac. Only thing i have changed recently, but actually changed back was to enter a DNS at my USB-Ethernet-Connection to connect locally to another mac in the network. But as i said, i deleted this DNS-Server again. Would be thankful for help. An i won't reinstall my mac completely from scratch either.