There might be other reasons for this error but this is what I found out:
You might get the error when you have a databound AJAX reorderlist and you are trying to persist the reordering using database.
The SELECT and UPDATE methods should have the same number of fields, even if they are not used in UPDATE, the signature of both the methods should be matching else you will get this error.
Here is very good article on how to use AJAX Reorderlist with ObjectDataSource by Justin Saraceno.
http://weblogs.asp.net/justinsaraceno/archive/2008/02/22/reorderlist-with-objectdatasource.aspx