Problem importing leads: custom field blank

Problem importing leads: custom field blank

Hi, I am trying to import about 1000 leads from a csv file.  I'm using the free edition.  I've created some custom fields in the Lead Field manager, and for some reason one of my custom fields does not import any information.  The other custom fields imported information just fine, but one is just completely blank for every imported lead.  I did not use any forbidden symbols or anything.  Any ideas what the problem is?

Thanks

atorresala