Fine black lines begin to appear on my viewfinder today as I switched my Nikon D90 on to shoot. Perhaps, they have been there all along...I am not very sure. They are not those lines you turned on via menu D2 - Viewfinder grid display but very fine horizontal/vertical black lines interconnecting the focus brackets at the center of the viewfinder.
I will be paying the Nikon Service Center today to find out if it can be rectified during lunch hour.
Will keep everyone posted what happens next...
UPDATED - According to the Nikon D90 manual - page 9, this situation is classified normal. Don't panic.