I am using family tree maker 2012 unfortunately although i have been taking regular back ups i did not know when the problem occurred so all the back ups have the same issues.
I have tried all the things that you have advised without success.
I do have one back up that is not affected but is over one year old so there is a lot of data that will have been lost if i can't manage a way to access the present file. I have checked the source information on the tree and the problem seems to lie with some files i have downloaded about the 1851 census. Any help at all with this issue would be very welcome.