Warning: Unable to read symbols for /Developer/Platforms/iPhoneOS.platform

Got mysterious warnings, while trying to debug an application in iPhone device. Used to work, but suddenly not any more! The only difference I can think of is that I'm using Facebook iOS SDK for the first time.

warning: Unable to read symbols for /Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.2.1 (8C148a)/Symbols/usr/lib/info/dns.so (file not found).

Copied "info" folder from 4.2 to 4.2.1, since it was missing. Ok.

warning: Unable to read symbols for /Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.2.1 (8C148a)/Symbols/System/Library/AccessibilityBundles/AccessibilitySettingsLoader.bundle/AccessibilitySettingsLoader (file not found).

Copied AccessibilityBundles folder from 4.2 to 4.2.1, since it was missing, too. Ok.

warning: Unable to read symbols for /Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.2.1 (8C148a)/Symbols/Developer/usr/lib/libXcodeDebuggerSupport.dylib (file not found).

Copied libXcodeDebuggerSupport folder from 4.2 to 4.2.1, since it was missing, too. Still get warning! Update: this article "libXcodeDebuggerSupport.dylib is missing in iOS 4.2.1 development SDK" at Stackover might help someone, but didn't help me.

Can't start debugger. CFSOcketSetAddress returns error '-1'
Try rebooting your device and/or Macintosh

Rebooted device. Ok.

Really wish I knew what's going on... Why did my SDK suddenly get corrupted? Or is it corrupted at all? Why does Xcode show me only iOS 4.2, there used to be more? Why does "latest" point to 4.2 instead of 4.2.1? What is difference between 8C148 vs. 8C148a?