[zebra 22903] can't setsockopt IP_ADD_MEMBERSHIP No buffer space available

Wonder if anyone can help me ... I have a Fedora Core 4 box running about
10-15 subinterfaces in RIPD, all works fine except for the last few
interfaces, then I get the following errors :

2006/07/03 22:51:46 RIP: RIPd 0.98.3 starting: vty@2602
2006/07/03 22:51:47 RIP: can't setsockopt IP_ADD_MEMBERSHIP No buffer space
available
2006/07/03 22:51:47 RIP: multicast join failed, interface eth0.2323 not
running
2006/07/03 22:51:47 RIP: can't setsockopt IP_ADD_MEMBERSHIP No buffer space
available
2006/07/03 22:51:47 RIP: multicast join failed, interface eth0.2326 not
running
2006/07/03 22:51:47 RIP: can't setsockopt IP_ADD_MEMBERSHIP No buffer space
available
2006/07/03 22:51:47 RIP: multicast join failed, interface eth0.2327 not
running

Have anyone seen this before and how can this be fixed. I have tried it with
2 different machines

Thanks
Andre