Not sure why this is required. You can add a number of different hosts in the fping command line. No need to use a hostfile. You should be able to use
$FPING_Results = invoke-expression "$FPING_EXE $PossiblyDeadComputers -p20 -n 3 -l 2>&1"
Do you have a crash address for version 2.22? The crash is probably related with the usage of the host file.
Reminds me I should release version 3.00. The beta seems to be running fine.