RH9: System freezes due to cyrus?

[Cornelius Kölbel <cornelius koelbel gmx de>]

Hello,

sometimes my system freezes. I am transcoding some video files, i.e. the 
system is at rather high load.
When I return to the computer, sometimes it is frozen.

I can´t do anything anymore, the mouse is not moving, the keyboard does 
not react, (I can´t even switch the num lock light).

Ctrl-Alt-Delete, does not work either.

I can see, that one of the last lines in the /var/log/messeges is:

ctl_cyrusdb[29254]: checkpointing cyrus databases
ctl_cyrusdb[29254]: done checkpointing cyrus databases

This happened a few times and always the message of the cyrus-imapd was 
one of the last one.

I never had this problem under R.H. 7.3

I am now running the cyrus imapd 2.1.13,

Under RH 7.3 I was running 2.1.12, which I had compiled on my own.

Any hints, what I can do to analyze the problem?
Anyone having a similar problem?

Regards
Cornelius