Categories gone in Units&Zone

[taralis]

Well literally list of categories in units&zone tab of drawing settings is empty. (See picture attached.)

What's even more strange it's happened on three machines out of five in our office.  No registry changes or significant system updates were made or at least updates were made on all five systems.All are versions of Civil 2012 (32bit) on Windows Vista SP2.

Any ideas? 

[taralis]

UPDATE:

Reinstallation helped.

Still would be nice to know the reason for this.

Thnx.

[taralis]

UPDATE 2:

Reinstallation has no effect on one of the three computers (with the problem described above).

PC runs Civil 3D 2012 on Windows Vista SP2