Single-Select query always returns NULL

Hello,

I have created a report in iReport 5.0.1 and it works great in the preview but when I upload to JasperServer and run the report, the column for the drop down always shows [NULL].  This is how my report is set up:

• Parameter Name = DiveGroup
• SQL Query in report:

SELECT caseid, owner, group
FROM cases
WHERE group = $P{DiveGroup}

• Input Control name = DiveGroup
  • Input control type = Single-select Query
  • Prompt text = DiveGroup
  • Parameter Name (read-only) = DiveGroup
  • Select a query from the respository = /Queries/DiveGroup
  • Value Column = DiveGroup
  • Visible Columns = DiveGroup
• Query for single-select query
  • Name  = DiveGroup
  • Resource ID = DiveGroup

I've double and tripled checked the 'DiveGroup' parameter and Input control and they are definetely the same.  I have even recreated the report and get the same problem.  I know my datasource is good because if I remove the parameter and WHERE statement in the report, the report generated just fine.

Can anyone provide any pointers or suggestions?

Many thanks