Error when running CONJOINT - "An undefined variable name, or a scratch or system variable was specified...."

Problem

I am using IBM SPSS Statistics and I receive the following error when I run a CONJOINT analysis from the syntax window. I have compared my syntax to the manual and and I am using the example of conjoing analysis provided in the Help System Tutorial. It appears to be correct. Can you tell me what is wrong? Below is an example of the syntax. CONJOINT PLAN='C:\Program Files\IBM\SPSS\Statistics\20\Samples\English\carpet_plan.sav' /DATA='C:\Program Files\IBM\SPSS\Statistics\20\Samples\English\carpet_prefs.sav' /SCORE= x1 TO x22 /SUBJECT=ID /FACTORS=PACKAGE BRAND (DISCRETE) PRICE (LINEAR LESS) SEAL (LINEAR MORE) MONEY (LINEAR MORE) /PRINT=SUMMARYONLY. Warnings Text: x1 Command: CONJOINT An undefined variable name, or a scratch or system variable was specified in a variable list which accepts only standard variables. Check spelling and verify the existence of this variable. Execution of this command stops. Unrecognized text appears where end of subcommand (slash) was expected.