Hatch Problem

[nuttynutter123]

I am trying to hatch some bits on one of my drawings.. the problme i am getting is that it wont let me use a scale any less 20? I am using AutoCAD 2008 if that helps. I cannot understand it. it has never done this before?
It is one of our standard details that sometimes needs to be changed and to change it i need to delete that hatching change a few fits on the drawing and then re hatch it. (its a trench detail)
Please Help
Thanks in advance!

[NBC]

It sounds like something to do with the MaxHatch variable.
the higher the value of this, the more dense your hatch patters can be.
to change the value of this:
1. At the Command prompt, enter (setenv “MaxHatch” “n”)
where n is a number between 100 and 10000000 (ten million).
Be aware when entering the text at the command line that MaxHatch is case-sensitive.

[SLW210]

If the Hatching is associative it should adjust itself as you make changes to its boundaries. No need to delete and rehatch.