"can't add existing file" on ProjectSettings .asset files

Every time I start up my project, I see an info message saying that all the ProjectSettings .asset files can't be added:

 //<depot_path>/ProjectSettings/AudioManager.asset - can't add existing file (level 48)
 //<depot_path>/ProjectSettings/DynamicsManager.asset - can't add existing file (level 48)
 //<depot_path>/ProjectSettings/EditorBuildSettings.asset - can't add existing file (level 48)
 //<depot_path>/ProjectSettings/EditorSettings.asset - can't add existing file (level 48)
 //<depot_path>/ProjectSettings/GraphicsSettings.asset - can't add existing file (level 48)

This is also preceded by a "Cannot set mode of files in offline mode" error, and a message that I logged out (even though I'm logged in).

Everything seems to work OK beyond this, I'm just very particular about eliminating warnings and suspicious log messages because I find they always come back to haunt (and I'm currently experiencing other problems migrating the project to Unity5 from 4, so I'm trying to eliminate all other possible problem spots). Is anyone else seeing this with Unity5 and Perforce integration? Any ideas how to resolve it?