Unrecognized custom attribute

[Das Goravani]

I am trying to insert a lookup record. I have this code:

Do tvO.$xdefine('dtbucket')
Calculate $ctask.tvdtbucketrow.bucklist as #L1
Calculate $ctask.tvdtbucketrow.buckc1 as 'EmailAttachmentTypes'
Do $ctask.tvO.$xinsert('dtbucket') Returns $ctask.tMyFlag

tvO is an object that is subtyped to another object that contains code.
$xdefine is a method that takes a database table name as parameter and just defines a row from a schema with the same name "sbucket" in this case
When I try to execute the first line of the above code it gives that error "Unrecognized custom attribute". 
The method only has one parameter. There are no other custom attributes here. 
I don’t know why it inserted $ctask on the second occurrenceof tvO in my code here and not on the first. I tried putting it in on the first, that did not help.

Why does it give that error "Unrecognized custom attribute".

What can I do to get rid of this problem. 

I've used these methods before with no problem. 

I’ve done things this way for a long time no problem in other library.