no concept column for row per obs data export

I'm trying to create a concept column for the hemoglobin of my patients through the row per obs data export. I've placed the given name on the first column but when I make a 2nd column which should have the hemoglobin, the only thing that gets saved is the 1st column which is a simple column. I've tried a lot of simple columns and they get saved but concept columns don't get saved.
The log of catalina.out shows the following:

INFO - LoggingAdvice.invoke(102) |2011-02-24 16:11:11,885| In method ReportObjectService.saveReportObject. Arguments: AbstractReportObject=Data Export #5,
INFO - LoggingAdvice.invoke(127) |2011-02-24 16:11:11,914| Exiting method saveReportObject
INFO - LoggingAdvice.invoke(102) |2011-02-24 16:16:57,494| In method ReportObjectService.saveReportObject. Arguments: AbstractReportObject=Data Export #5,
INFO - LoggingAdvice.invoke(127) |2011-02-24 16:16:57,514| Exiting method saveReportObject