Could it be possible that they are trying to run your application under VFP8?

>In one customer site my VFP 9 application causes error
>
>Variable '_REPORTOUTPUT' is not found.
>
>at line
>
> DO (_reportoutput) WITH 5, olistener
>
>
>I'm unable to reproduce this in my development computer. In other customer sites the error does not occur.
>
>Any idea how to fix this ?
>
>I have the following code in my application init code to include all required components into exe file:
>
>SET ENGINEBEHAVIOR 90
>SET REPORTBEHAVIOR 80
>_REPORTBUILDER = "frxbuilder.prg"
>_REPORTPREVIEW = "frxpreview.prg"
>_REPORTOUTPUT = "frxoutput.prg"
>EXTERNAL PROCEDURE frxbuilder.prg,frxpreview.prg,frxoutput.prg