cyrus murder- lost connection errors

[Vladimir Nikolic]

Hi,

I have the following cyrus murder configuration:
frontend - cyrus-2.3.7 on RHEL 5
murder server - cyrus-2.3.8 on FreeBSD 6.2
backends - cyrus-2.3.7 on FreeBSD 6.1 and cyrus-2.3.7 on RHEL 5
There are somewhere about 50000 users (40000 on FreeBSD and 10000 on RHEL).
POP3 users are complaining that they have to type their passwords 
several times before they finally get access to their mails. Some time 
after that they are again asked to enter password to log into server.
Maillog on frontend are full of lines:
Oct 20 22:56:35 imap2 imap[12440]: Fatal error: Lost connection to 
selected backend
Oct 20 22:56:35 imap2 imap[11320]: Fatal error: Lost connection to 
selected backend
Oct 20 22:57:26 imap2 pop3[11611]: Fatal error: Lost connection to input 
stream
Oct 20 23:01:27 imap2 pop3[23448]: Fatal error: Lost connection to input 
stream
and
Oct 20 23:11:04 imap2 master[3605]: service lmtp pid 31838 in BUSY 
state: terminated abnormally
Oct 20 23:11:04 imap2 master[3605]: service lmtp pid 28093 in BUSY 
state: terminated abnormally
Oct 20 23:12:04 imap2 master[3605]: service pop3 pid 20089 in BUSY 
state: terminated abnormally
Oct 20 23:12:59 imap2 master[3605]: service pop3 pid 19554 in BUSY 
state: terminated abnormally
Oct 20 23:13:47 imap2 master[3605]: service imaps pid 1032 in BUSY 
state: terminated abnormally
Servers are attached to the network by 2 switches (100Mbps full duplex) 
which are not congested. Loads on servers are relatively small.
Did someone have similar problem? Would  upgrade to 2.3.9 help?

Thanks,
Vladimir