Hi:
You are probably using the DATE variable in a CLASS statement (or else you're selecting it as the classification variable) in your task. I can duplicate your issue with code.
[pre]
data testdate;
set sashelp.prdsale;
** month IS a SAS date, but formatted to MonName3;
** so create an explicit date variable and a character date variable;
date = month;
altdate = date;
chardate = put(month,monyy7.);
format date monyy7. altdate date9.;
run;
proc print data=testdate(obs=15);
var prodtype date altdate chardate actual;
title 'proc print using formats assigned in data step';
run;
ods listing;
proc means data=testdate;
title 'compare date formats used to proc print of data';
var actual;
class date altdate;
format date monyy7. altdate date9.;
run;
proc means data=testdate;
title 'using character version of date';
var actual;
class chardate;
run;
[/pre]
But duplicating the problem doesn't really help you. The workaround that I show in my code is to create a character variable that contains the date formatted with MONYY7 and then use the character variable as the CLASS variable in your summary statistics task. Or just switch over to a code node and submit the proc means code once you create the character version of the date.
However, I think your best bet for help with this problem is to contact Tech Support. There's something odd happening and Tech Support is the best place to go for help.
To find out how to contact Tech Support, refer to:
http://support.sas.com/techsup/contact/index.html
cynthia