Environment: NW 6.5, Zfd 4, eDir 8734

I'm trying to rename an imported workstation from:

SY13-01-SITEA - XX:XX:XX:XX:XX:XXWIN2000
to:
SY13A-01-SITEA - XX:XX:XX:XX:XX:XXWIN2000
and I keep getting the following error:
Invalid Character(s) in Object name

What am I missing?