Assura LVS JoinNets segmentation fault

Hi,

I've tried to add a "joinNets" specification to assura LVS. I've done this from Virtuoso Layout in Assura -> "RunAssura LVS" -> "Modify avCompareRules" -> "Network" ->joinNets. I've added the text:

joinNets("SN") 

with the effect that it lists an extra avCompareRule which appears as:

:lay: joinNets("SN")

When I run it fails, with the following at the end of the log file:

Starting Nvn PreExtraction...

Starting /home/cdsmgr/Assura/tools/assura/bin/nvn /home/sim/Cadence/ASSURA_LVS/DFlipFlopSafeSetResetBufferedSqueezedChokedLowNClk2Out/DFlipFlopSafeSetResetBufferedSqueezedChokedLowNClk2Out.rsf -preExtract -exec1 -libdefs /home/sim/Cadence/lib.defs -cdslib /home/sim/Cadence/cds.lib
@(#)$CDS: nvn version av3.1:Production:dfII6.1.2:IC6.1.2.149 05/27/2008 17:23 (sfrh41) $
sub-version 317_USR2_HF7, integ signature 2008-05-27-1126
run on teodev1.iss.infn.it at Sun Apr 25 20:30:34 2010
Loading all available p-cell functions
AMS_DB set to cds
No mx check
ROD pcell code loaded

Finished /home/cdsmgr/Assura/tools/assura/bin/nvn

*WARNING* An error occurred during Nvn PreExtraction.
LVS preprocessing requires a successful run of Nvn.
Assura will now terminate.


*WARNING* /home/cdsmgr/Assura/tools/assura/bin/nvn exit with bad status
*WARNING* Segmentation Fault
*WARNING* Assura execution terminated
*WARNING* Bad exit from child process .. 0x100


*****  aveng terminated abnormally  *****


*WARNING* aveng exit with bad status
*WARNING* Status 256
*WARNING* Assura execution terminated


*****  aveng fork terminated abnormally  *****

When I remove the specification it works fine, and this is repeatable, even after restarting cadence. Can anyone suggest what the problem might be?

Thanks very much,

 Sim Bamford