dtrace discuss - Sep 2009 - dtrace: error on enabled probe ID 1 (ID 31450: fbt:ip:tcp_rput_data:entry): invalid address (0x0) in predicate at DIF offset 36

I''m trying to set a point in which to run a series of commands when the
TCP receive window size hits zero.  I''ve found this works on my cluster
node (118833-36) and an opensolaris host.  But on other servers (T2000, 
Ultra 45 Workstation(127127-11), ) it does not work.

fbt:ip:tcp_rput_date:entry
/((conn_t *)arg0)->conn_tcp->tcp_rwnd == 0/
{
   printf("pipeline full or window closed %d\n",
        ((conn_t *)arg0)->conn_tcp->tcp_rwnd);

/*
    stuff goes down here to stop the application and run
    a series of commands
*/

}

I get this error.

dtrace: error on enabled probe ID 1 (ID 31450: 
fbt:ip:tcp_rput_data:entry): invalid address (0x0) in predicate at DIF 
offset 36

Any pointers or different approaches?

Thanks

Dave