Why can't Spatial Analyst add???

Discussion created by Cyndy on Oct 5, 2010
Hi Folks -

My installation of Arc GIS 9.2 is acting bizarre.  I am trying to do a bunch of raster calculations, ie, adding, multiplying, scaling, etc. using the raster calculator.  I am obtaining nonsense results;  for instance, adding a small float value to a raster, and getting huge numbers back that I know are wrong.  I've never had this problem before!  I have tried the toolbox and the SA calculator; same results.  Tried my original *.img file then converted it to an ESRI grid, same results.  I am at a loss to understand why Arc suddenly up and forgot how to do simple math!  Any advice for me? thanks.