I have a rather bizarre error message.

Anytime I use the measure window and try to change the units (i.e. from millimetres to metres) I get an error message telling me to please enter an integer from 2-256.

Needless to say, it's a pointless error message, I'm in a window with nowhere to enter an integer.

This is SW2009SP5.  I don't know when exactly this started as until recently most jobs were fine in millimetres.