You're passing strings by reference for parameters DECLAREd as passed by value.

>The declaration is
>

>declare integer  BUICScan  in BUICAP32.DLL integer iJobType, ;
>                             string lpFront, string lpLenFront, ;
>                             string lpBack, string lpLenBack, ;
>                             string lpCode, string lpLenCode
>

>the calling code is:

>    m.nretval=buicscan(THIS.nscan_opt,;
>      THIS.cfront_fn, ;
>      @temp_cfront_len, ;
>      THIS.cback_fn, ;
>      @temp_cback_len, ;
>      @temp_cmicr_text, ;
>      @temp_cmicr_len)
>

>with the values translating to:
>=buicscan(5,"F.TIF"," "," "," "," "," ")
>
>It takes about 3 seconds and then bombs with the "dll caused exception"
>
>Please tell me what the obvious thing I'm missing is.