Yes/No sometimes won't allow updating!

I have a form that has worked great for 5+ months. Two days ago, I changed
ONLY the position of a Yes/No box from the bottom of the row to the second to
top. I changed my tab order, and all was well. Three new records in, when
trying to use the space bar to tick this box yes, I receive an error dialog
that says "Field cannot be updated". I have checked the properties and
ensured that it is not locked. I can not click nor use the space bar to tick
it.
However, if I close it or the entire database program, more times than not,
when I reopen it and try again, it works just fine... for a while.
I have tried deleting the control and adding it back in, to no avail.

I have no clue why it's doing this. Any ideas?

--
Message posted via AccessMonster.com
http://www.accessmonster.com/Uwe/For...forms/200904/1