This started happening a few weeks ago (at least I noticed it then) on a
quite busy database. happens from once every 2-3 days to  once or twice
a day.

Is it a known problem ?

(gdb) bt
#0 0x4028158f in strlen () from /lib/libc.so.6
#1 0x520f6a47 in slon_quote_literal (str=0x0) at slony1_funcs.c:1073
#2 0x520f5dcd in _Slony_I_logTrigger (fcinfo=0xbfffde60) at
slony1_funcs.c:762
#3 0x082445b7 in fmgr_internal_function ()
#4 0x08111f9d in FreeTriggerDesc ()
#5 0x08113316 in ExecARUpdateTriggers ()

It happens for normal insert/update query (in a pl/pgsql function), and
does not happen when I run that function again.

-- 
Hannu Krosing <hannu at skype.net>