I had this problem when VFP 3.0 came out. The way I use to fix the problem was export the table in VFP to a FoxPro 2.X .DBF.

When I realized what was happening I made a list of all table in Foxpro2.X and never opened them in VFP. The culprit was a staff member not knowing about the automatic conversion of the DBF header when opened in VFP.