Dimensioning problem

I'm quite new to DraftSight.  I have stumbled through creating a drawing and now I want to apply dimensions to it.  For some reason when I use the linear dimension command all I get is three lines.  No arrows, no value, no offset from the drawing.  When I start DraftSight with a new drawing, draw a rectangle, and dimension it everything works as I expect.  But when I open my drawing it doesn't work.  Something must have been changed in the Format  - Dimension style settings, but I can't figure out what is wrong.  Is there some way to set all the dimension style settings back to default values?  I don't want to have to spend several hours re-entering my entire drawing just to get dimensioning working.

Thanks in advance for any help.

- Stephen Porter