A few days ago I “played” a little bit with my Android phone. The next day I recognized that several of my accounts have disappeared. I added two of them again. It took some time to find out that they always get lost after a reboot. So what happens?
First I thought that it has something to do with Hangouts, Google’s replacement for Google Talk. I deinstalled it but nothing changed.
The reason for this problem is that if an application which provides accounts to the system — such as e.g. the Twitter app or the Email app — is stored on the SD card instead of the built-in flash drive. In that case Android cannot read the account information during boot. This is because the SD drive is mounted in a too late stage of the boot process.
To solve this move the app back to the phone: Settings -> Applications -> Manage applications -> <app> -> Move to phone.