data input method seems to be failing, but why?

This is how my data input method is defined:
/bin/sh <path_cacti>/scripts/icmp-fw-hops.sh <hostname>

This is how it looks like in the log:
03/05/2013 03:00:02 PM - SPINE: Poller[0] Host[406] TH[1] DS[11697] SCRIPT: /bin/sh /usr/share/cacti/scripts/icmp-fw-hops.sh , output: 0

As you can see, there's something missing, the hostname. Any ideas on how to debug and/or solve that? 

-andreas

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