Quick reminder to myself when you define a block you can give it units mm, m , or make it unitless.
If someone draws a block of say a title block at 800 units by 400 units and then sets the blockunits to m by mistake when the block is inserted into a drawing with the drawings units set as mm the block will be made 1000 times bigger and you will scratch your head for a while to figure it out. To change the block units use
BMAKE (not BEDIT), select the already defined block in the pull down menu. Reset the units and exit.