Update available message: won't update or go away

After logging into the client, there is a message that an "update is available" with the option to "restart now". If I click restart now, the client closes and reopens at the login page. There is no patching attempt. I am able to play the game normally, so there doesn't seem to be anything critical missing (if anything at all). I have tried reinstalling the game twice, including on different drives on my computer, to no avail. This message is there every time I log in.