Linq + Failed to set one or more properties on type

So I have had quite an interesting hour or so tracking down the following Linq error:

Failed to set one or more properties on type [namespace].EntityContexts.project. Ensure that the input values are valid and can be converted to the corresponding property types.

This was occurring whilst performing an update in a formview. Previously the form had been behaving properly, but this morning I added a new field to the database and updated the LinqtoSQL file. I also added a new databound field to my formview, however since this every time i tried to update the form it crashed out.

A few people have suggested to delete your LinqtoSQL file and readd, this didn't work for me, I even created a new page with just the datasource and formview for testing purposes.

The datasource was configured to select all from a table and had auto insert, update delete set. The formview was just generated.

It was at this point that I noticed the foreign key relationships I had setup were child entities in my entitycontext. This meant that my formview was generating databound controls for my lookup table etc. In my original page these didn't exist as I had manually removed them in sourceview.
So I again removed these controls within my new page and tried again, still no joy, I then wondered if removing them in Design view instead of Source had any impact, and it did. What was happening was my designer code file was not being updated upon rebuilding from the pages source view.

I then thought further on how to avoid this, my initial thoughts were upon inserting a LinqDataSource only select the columns you need, thus skipping the child entities, this would work for read only select data sources however to use auto generate insert and update you can't use select. If you try to do this then you get the following error:

LinqDataSource 'LinqDataSource1' does not support the Select property when the Delete, Insert or Update operations are enabled

There is a way around this though, although its not pretty and i think its a massive bodge but, insert your datasource and manually select the columns you need, create your formview. Then update the datasource, you are now able to turn on auto gen insert, update and delete. However the manual select still exists on your datasource so switch to source view and remove that.

You should then finds it all works...... Total bodge, I'd sooner just ensure i switch to Design mode to remove my extra fields, but hey everyone has there own way...