What version of the Kobo firmware did you update to? Was this done after a factory reset?
The OCP packages do not install NickelMenu. You would need to install it separately. The error message you are getting is, I seem to remember, tied into KFMon not being installed. See
this message and
the response in the Kute File Monitor thread.
Are you using the scripts in the 2nd message of this thread to install the packages or are you using the .zip file directly? If you look at the .adds/nm directory do you see a file called koreader? One called kfmon? Did you reinstall KFMon from the standalone KFMon install package from the first menu?
You could try adding this line to NickelMenu's config file instead of trying to use KFMon to launch KOReader:
Code:
menu_item : main : KOReader : cmd_spawn : quiet : exec /mnt/onboard/.adds/koreader/koreader.sh