Dimension problems moving from V20 to V21

I am having dimension problems moving from V20 to V21
I am attaching 2 jpeg images to illustrate my problem.
The dark panel shows the properties of a 1:10 annotative dimension correctly inserted.
The Light panel shows the properties of a 1:10 annotative dimension incorrectly inserted
You will notice in the Light panel (v21) the property of arrow size has been scaled to 1/10th of the size that it should be. In the dark panel (v20) the arrow size is is 3 which matches the dimstyle i am using.
Both of these dimensions have been inserted using the same drawing loaded into the respective versions using an annotative scale of 1:10.
Can anyone tell me what global variable is making this change? and how to fix the problem.