Cannot get gridview update to work

[Wombleuk]

I've looked at various posts in this group, but have not found a
satisfactory answer.

I have created a table and populated it it with some data.
I created a new page, a sqldatasource, a gridview and wired them up.

I can display data and delete rows, but when I change an item via the
edit link, an update ostensibly occurs, but nothing changes.

I've created a breakpoint in onRowUpdating and examined the oldvalues
and newvalues; both are the same.
It would appear that the newly entered value is not getting passed back
to the sql that performs the actual update.

Is there a way I can track what is happening after I click the 'update'
link?
I've seen mention of profiling the database to see what is passed back,
but I have no idea how to do that.
tia
Graham