If you inspect the SAS-generated file (not using Excel), you will see that the data rows are generated correct and complete. The issue is with how Excel is interpreting those data rows and the imbedded "%" character under specific circumstances.
Investigate techniques for influencing how Excel is to interpret the SAS-generated file.
I found a related technical/conference paper at the SAS support
http://support.sas.com/ website using the SEARCH facility:
Using ODS to Generate Excel Files
Chevell Parker
http://support.sas.com/rnd/base/ods/templateFAQ/Excel1.pdf
Scott Barry
SBBWorks, Inc.