I found the answer and hope this helps anyone.......
1. My original model builder had no joins in the process. From that the model was published as a geoprocess to the server. The flex application using the geoprocess passed parameters to it without "QUOTES" around the column names. This process has always worked without any issues.
2. Based on the above results, I used the same methodology in my model builder but added a JOINS. However, passing the parameters to the geoprocess service without "QUOTES" will not work. Come to find out, this is consistent with the ESRI documentation stating that shapefiles and geodatabase queries need the columns quoted.
Maybe someone knows the answer as to why the geoprocess will work in situation number 1, but not in number 2. However, for future reference anyone running queries to a geoprocess; make sure you "QOUTE" your column names.
Eddie Q