Load balance and arp

hello, everyone!

i have 2 w2k3 servers, each server has one NIC:
server a ip: 192.168.1.1
server b ip: 192.168.1.2
virtual ip for NLB: 192.168.1.3
the cluster was configured in unicast mode and i noticed that it caused slow
traffic through switches, then i deleted this unicast mode cluster and creat
a new multicast mode cluster.
the new multicast mode cluster was created successfull, i can ping server b
(dedicated ip 192.168.1.2) from server a, and can ping server a (dedicated ip
192.168.1.1) from server b, but after 20 minutes, network load balance
manager report that host (server b)unreachable, when i check the arp table at
server a, i found that there is a static entry bind 192.168.1.2 to a mac
address, this mac seems like the virtual mac previously used for unicast mode
load balance. at server b, when i check arp table, i found the static entry
that bind 192.168.1.1 to that mac too, so the 2 servers can not communicate
with each other. i have tried to delete the static arp entry at 2 servers,
the commuication restored, but 20 minutes later, the static entry will come
back again, i'm realy confused and any suggestions will be appreciated! think
you all.