Excel - Define cell name not available

I have a problem with two PC systems (all other systems are ok). In Excel the option to define cell names from the menu Insert->Name the option is greyed out and will not allow to define this way. I can define names from the cell anme box. This issue happens on existing workbooks and any new ones created

Does enyone know why this option would be unavailable? The workbooks are not protected, I have checked for Disabled items (none disabled) and have done a Detect and Repair.

One system is running XP the other W2K. Both are running Office 2003