It's VFP9SP1 bug with FSEEK() on unbuffered file. The workaround is to open file in the buffered mode, as you already found.

>
>I have a old application that use to work fine until I (think) updated VFP9 SP1.
>
>I need to go to the end of file (TXT) and then, skip -410 positions, and then write something new.
>
>The code that always (until now) worked fine is below:
>

>nFile = FOpen("FILE.TXT",12)
>FSeek(nFile,-410,2)
>FPuts(nFile, "MY NEW TEXT HERE")
>

>
>Now, maybe after update my VFP9 to SP1, I have to do that:
>

>nFile = FOpen("FILE.TXT",12)
>FSeek(nFile,0,2)
>FSeek(nFile,-410,1)
>FPuts(nFile, "MY NEW TEXT HERE")
>

>
>Strange.... :-)
>
>Any comments.