(racoon 940) Repeated error message on VPN server's log

Hi all,

I'm using FreeBSD 4.11 with the latest racoon port (racoon-20040818a_1) 
and the VPN device
I connect to (a NetScreen firewall/VPN) sends a bunch of error messages 
to my sys admin that look
like this:

[00001] 2005-04-15 13:47:09 [Root]system-alert-00026: IPSec tunnel on int
ethernet3 with tunnel ID 0x80aa received a packet with a bad SPI.
xxx.xxx.xxx.xxx->xxx.xxx.xxx.xxx/120, ESP, SPI 0xc752f16d, SEQ 0xc

Any idea what might be causing these messages?

Thanks.

--Chris