Custome Columns didn't render

Question

in my list i have used to use parent , child drop down list columns for three level 'parent , child , child'
which read from different list but joined together , in new form to add text boxes and change their type to list from field
then all controls in my form give me same  message that there an error when fetching preview an error occurred when fetching preview

Answer 1

How many lists are involved in your scenario?  What are their names? How many lookup fields do you have on each list? How are the lists related to each other with lookup fields? What do you mean by read from different list but joined together? Are you customizing the newform.aspx for the list with Data Form Web Part?

Answer 2

in my case i use them in newform.aspx  for the list with data form web part .

for this scenario every custom column we load all list and then choose parent list and what we want for the column in parent in child one we load all list and choose one to be child and then choose parent list and column that join to lists this the same what i do for child child column but after changing type of text box to  list from field  i get this 'Error'