Hi Kevin,
I don't know what caused your error. For some reason the code in db_exec_plsql delete_group
is failing, but your snippet doesn't contain the actual error.
Check in your error log again. Just before the snippet that you posted, there should be another error that is the actual DB error. That might be more helpful.
Also, it's a good idea to put error log snippets in <pre> tags so that they're easier to read.