foxpro & sco 6.0

My problem is the following:
I have installed Foxpro 2.6 for Unix, in HPCOMPAQ ML350 G5 with SCO 6.0, and when the application is executed in FoxPro, the following message appears: "file is in use" , but there is nobody else working.

check to make sure that permissions are 0666 on the .dbf