Hi,
In the Applications folder right click the app itself and chose "Show Packages Contents"
This will change to show you the Contents Folder.
This contains a Resource folder as well as others.
There will be a folder for Dutch. (.lproj)
The Resources folder also contains the Sounds and Pics that are used to display the Buddy List, Chat windows, interface and so on.
There are also what are called .nib files that are subroutines for the actions that the app can do.
You cannot see inside these.
It may be that you have to use the Restart with CMD + R to Restore the OS and the Apple Apps to sort this issue.
8:56 pm Tuesday; December 3, 2013
iMac 2.5Ghz 5i 2011 (Mavericks 10.9)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad