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 ?

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?