When i try to load a engine soundfile for the FZ5 only FXO
sounds will appear in list.

If i recall correctly, i did the following to get this bug:
I was driving a FZ5. Then i changed the player cam to a FXO driver.
I opened the engine editor and made some changes. Opened the save file
dialog and entered a name for it. But, before i pressed the OK button, the player pitted and the camera got back to my FZ5. Then I pressed OK to sve the file. But now, I am not longer able to load a FZ5_*** file when driving the FZ. Only FXO_*** files will appear in list. The fz-sounds do still exist in the engine folder.

bye
-chuck

yay. At least i found a solution without reinstalling the game

Switching the player-profile)