
you can see that the names do not match... the names and numbers on the top are absolutely correct. i think i have found the issue:

when i select the "DataSource > Relation 1 > Username" field to be in the "Argument Data Column", it incorrectly reverts to the "bpUser > UserName" field instead. that is the field where the data is linked from, but it is not keeping the "relation".
i attempted to reproduce this in your stand alone report creator, designer.exe, but it correctly saved the "relation" and correctly displayed the "arguments"

thanks
erik