Hi Kara,
Nick's suggestions are spot on but there might be a bug with ConvertDset for that particular command you are running. I am not sure what is causing the errors you got with ConvertDset. I am on vacation until Tuesday so I can't look into it much before then.
For the moment, it might be easiest that you rerun at least one of your afni_proc.py commands with the added regression analysis options. Just make sure you use one of your standard meshes spec files that were created by @SUMA_Make_Spec_FS. You can at least take a look at the generated script to see how we string the commands together and either do something similar or rerun all of your subjects again.
cheers,
Ziad