Today I tried updating Evernote ... and afterwards, it wouldn't open (or let me reinstall it). Here's the solution that worked for me: Background: I attempted to update Evernote (on my mac) to the latest version, 5.0.2 (from 5.0.1). I downloaded (and ran) the update. It showed "migrating notes" ... but once it finished, Evernote never opened. I tried rebooting and that didn't help. I tried deleting Evernote & re-downloading the latest version and that didn't work either. Below are TWO different solutions that I got from Evernote support - the first one DID NOT work for me. Fortunately, the second one did - BUT - there is a drawback to method #2 (you'll need to resync everything back down). In any event before doing either, chat with Evernote support first to see which (if either) they recommend for you: Method #1 - (this didn't work for me, but might for you): Quit Evernote from the elephant icon in the Menu Bar Drag the Evernote application to the system Trash Reboot your Mac Download and install the latest version of the Mac client: http://www.evernote....ile=EvernoteMac When you open the download, make sure to drag the Evernote icon into the Applications folder instead of running it from within the installer package. Eject the disk image and delete the installer file before you run Evernote. Method #2 - this one DID WORK for me: (but if you go this route, be advised that Evernote will be empty and you will need to re-sync everything back down). My Evernote is many gigs in size, and is still syncing several hours later - but - it is nearly 75% done and looking fine). Here's method #2: Don't forget that while we work on this you can access your synced notes online at www.evernote.com. We would like to have you completely delete all traces of Evernote and then try to install again. First verify that all your notes have synced. If you have unsynced or local only notes you will need to export these and back them up in another location prior to uninstalling Evernote in this manner. Failure to back up local only or unsynced notes will result in the loss of these notes. Once ready, please download and use the following program to uninstall Evernote: http://onnati.net/apptrap/ Reboot your computer. Once you’ve rebooted, Simply drag the Evernote application to the Mac Trash and AppTrap will detect that you are uninstalling and remove all the correct files. Reboot your computer. Then, download and install the latest version of the Mac client: http://www.evernote....ile=EvernoteMac When you open our installer, make sure to drag the Evernote icon into the Applications folder instead of running it from within the installer package. Eject the disk image and delete the installer file before you run Evernote. Many thanks to Evernote Support - you guys are awesome!