Hey Lotruth,
Client variables depend on the browser sending a valid cfid/cftoken pair via cookies. I would check to make sure that NS has cookies enabled as that's about the extent of the browser's involvment with client variables. If the browser has cookies enabled and it still doesn't work, you might want to clear out all the cookies by removing the cookies.txt file and have it generate new ones as it's possible (but very unlikely) that they've become corrupt. This will of course delete all cookies for other sites so make sure you really are ok with this before removing the cookies file.
Good luck,
GJ