Snap/Increment Key Deisabled

Hello, and yes this does make me feel noob, but it is a first for me and have not found a solution.

When moving vertices, the ctrl key no long works for both snapping and increments.

I have probably done something stupid to disable it, but cannot find any way to re-enable it.
Help would be appreciated.

Is the transform snapping option set to increment ?
http://wiki.blender.org/index.php/Doc:2.6/Manual/3D_interaction/Transform_Control/Snap_to_Mesh#Transform_Snapping

Show us your settings and blend file

Yes every thing was fine, I had good control over all directly related settings.
I found that it did not work whilst in the metric system. Odd. Set it back to Default and everything works fine again.
Possible bug?