Yuseff,

ntx filesa re clipper index files similar to IDX files in VFP. VFP does not support the clipper NTX index format and so it will not keep these files up to date with your data changes. That is probably why you are getting errors in the clipper program when have modified the data with VFP.

Check in the application for a reindex option. If there is one then after you modify the data in VFP you will need to do the reindex option in the clipper application to get the index files back in sync with the data.