[EMBOSS] "Invalid XY graph value 'png' "

[Ulrike Kaule]

Hello,

I want to use EMBOSS-programm 'iep' in Taverna - but when running it, I 
get the following error message:

...
Exit: 1

Devices allowed are:-
postscript
ps
hpgl
hp7470
hp7580
meta
colourps
cps
xwindows
x11
tektronics
tekt
tek4107t
tek
none
null
text
data
xterm
Error: Invalid XY graph value 'png'
Died: iep terminated: Bad value for '-graph' with -auto defined
...

Is there any possibility to turn off this graphical mode in acd-file?  
Or do I have to install something else (graphical drivers, etc.)?

Thank you in advance

Ulrike Kaule

P.S.: The version of EMBOSS is 3.0.0. and it is running on Linux-machine.