> Yes, this is the identical result I get on Windows XP, with Csound 5.06.
> 
> Also, if possible, I need a version that allows a soundin.N (integer) input 
> to the UDO.
> 
> Perhaps once we get the main issue sorted, this latter request will be 
> easily solved.
> 
> Art Hunkins

The error with ftgen avoids the crash with 5.06.
Updated example:

<CsoundSynthesizer>
<CsInstruments>
sr     = 44100
ksmps  = 64
nchnls = 2

;; filevalid for csound < 5.13 (tested with 5.07)
opcode filevalid_S, i, S
  Sfile xin
  ires ftgen 2012, 0, 2, 1, Sfile, 0, 0, 0
  xout ires - 2011
endop

opcode filevalid_i, i, i
  ifilcod xin
  ires ftgen 2012, 0, 2, 1, ifilcod, 0, 0, 0
  xout ires - 2011
endop

instr 1
Sfile = "dindondan.wav"
ires filevalid_S Sfile
if (ires != 1) igoto end
al soundin Sfile

ifile = 1
ires filevalid_i ifile
if (ires != 1) igoto end
ar soundin ifile

outs al, ar
end:
if (ires != 1) then
  turnoff
endif
endin
</CsInstruments>
<CsScore>
i1 0 1
e
</CsScore>
</CsoundSynthesizer>