The following patch fixes the crashes I experienced.
/Mikael
--- ./wifo/eXosip/src/udp.c.orig 2007-06-27 13:10:55.000000000 +0200
+++ ./wifo/eXosip/src/udp.c 2007-06-27 13:12:11.000000000 +0200
@@ -1676,8 +1676,11 @@
strncpy(je->sip_event,event_hdr->hvalue,sizeof(je->sip_event));
if (je->msg_body)
osip_free(je->msg_body);
-
- je->msg_body = osip_strdup(body->body);
+
+ if (body)
+ je->msg_body = osip_strdup(body->body);
+ else
+ je->msg_body = osip_strdup("");
if (je->msg_body == NULL) {
eXosip_event_free(je);
