Hello,
No that was not the answer, but ome fields you will not be able to change. And I wanted to find out if you were trying to change one of those fields that sharepoint "locks up".
If you want to change the type of a column field to choice you do that by going to:
Documents and Lists -> Click on the list you want to change -> On the left side under Actions, select Modify settings and columns -> On the Customize page under Columns, click the Column name you want to change.
But as I said in my previous post, some of the fields (for example the one having "Linked to item with edit menu") you will not be able to change the field type.
When you create a list or import a list, atleast one of the columns will not be editable more than changing for example the number of characters you can enter (if it is a single line tex or multiple lines of text)nor can it be deleted.
Regards,
Thomas