CARP and spontaneous switching between MASTER - BACKUP

[dmitry surovtsev]

Hi all, 

Did anybody face the problem with spontaneous switching between MASTER - BACKUP carp machines? 
The configuration is: 

First computer (MASTER): 
sysctl net.inet.carp.allow=1 
sysctl net.inet.carp.preempt=1 (or 0, it doesn't matter) 
sysctl net.inet.carp.arpbalance=0 

ifconfig carp0 create 
ifconfig carp0 vhid 1 advbase 1 pass pass1 192.168.1.1/24 

Second computer (BACKUP): 
sysctl net.inet.carp.allow=1 
sysctl net.inet.carp.preempt=1 (or 0, it doesn't matter) 
sysctl net.inet.carp.arpbalance=0 

ifconfig carp0 create 
ifconfig carp0 vhid 1 advbase 2 pass pass1 192.168.1.1/24 

Both computers are connected by direct cable (one pair of network cards with IP, say 192.168.2.1 and 192.168.2.2). 
Another network card of each copmuter has IP 192.168.1.1. 

The problem is: 
When i go to my squirrelmail web application by typing https://192.168.1.1 
i got a connection with master computer indeed. 
I type a login and password and then go to my Mailbox. 
After some time however I got an error from Squirrelmail: 
"You need to authorized to have an acces to your mail", then Squirrelmail 
proposes me to enter login and password again, second time. 
I do that and then have an access to mailbox, BUT on the second, BACKUP, server. 

ifconfig shows that first computer is still in MASTER mode, 
and the second is still in BACKUP mode. 

What may be the problem? 

Thanks in advance, 
Dmitry