I am trying to run PROC GENMOD using CLASS statements to define several variables. On some, but not all variables, I get the error message that "variable x has only one level". I know they all have 2-3 numeric levels. I am using SAS 9.1.3 with service pack 4, and I have run hotfixes for known issues from ftp://ftp.sas.com/techsup/download/hotfix/e9_win_sbcs.html#ba specific fix E9ST10 for Windows. Any idea why this is happening or how to fix this would be extremely appreciated. I have lost too many days of work already trying to solve this.