I was having trouble this past year with disappearing icons in the K2 player. I finally contacted NI tech support. They offered a few of suggestions that I thought I'd share with everyone. The last one solved my problem.
1. When you go on "Options" within the software under the tab "Load"
you can set a path. Please set this one to the:
.....Native Instruments\Kontakt Player 2\UserPatches folder.
2. When you click on the icon bar at left hand and you click on "Info"
e.g. in the JABB library. There you can set a path as well. Make sure that it
is on the correct location (in my case it is ...\Garritan\Jazz and Big Band
KP2 Library). After reseting these path, start KP2 again.
3) If that did not help, please try the following. Inside each library
folder you will find a file called "...info.nkc", e.g. "Jazz and Big Band
KP2_info.nkc". Note, it is a different file then the "...info.nkx" I was telling you about before. Delete this file and start Kontakt Player 2 again.
(I just renamed the file, and this worked for me. It also brought back the GPO icon.)