This is a sign that you have denied informant access to Keychain.  To resolve this please do the following in order.

1. Delete the informant sync account in informant preferences>accounts>informant sync (don't just logout).
2. Go informant menu> Preferences > ">>" then Advanced. Once there Press Reset Cache then press Toggle helper in that order.
3. Quit informant
4. In the Keychain Access app select the login keychain. In the list that shows up there should be an entry labeled "DesktopInformant", please right click and select delete from the drop down.
5. Start informant and go back to press the button labeled toggle helper
6. Add your informant sync account back in, login and complete a sync.

*Sometime in this process there may be a popup asking for permission, please select "allow always".