Thank Evan I think I solved my problem
I found a virus on a workstation and I think it corrupted VFP Exe. I reinstalled VFP and after that I haven't had more thouble.

>Some thoughts:
>
>- are you sure you set relation command is correct?
>- delete then recreate your indexes with delete tag all (you might want to write down the expressions if they are complex)
>
>>I have a database with about 90 tables
>>In some occasions when I use Set Relation To, the child table doesn't move with the parent table.
>>
>>I have reindexed many times all tables. Also I have used VALIDATE DATABASE RECOVER wit out solving the problem.
>>
>>If I free a child table from the database, it's works correctly, but When I put the table inside the database it doesn't work again.
>>
>>I'm using VFP 6.0 with Novell 4.11 and I'm using Fox since FoxBase and it's the first time I have this kind of problem
>>
>>Thanks in advance
>>
>>Carlos Restrepo