Sudden named process down

[Hisashi Kumada]

Hi,

I manage DNS server for some ISPs using Bind8.2.2 P5 on Solaris2.6.
The other day I found the named process down on one of them.
The system message file reads like this;

    Mar 22 19:32:00 host named[782]: flushset: out of memory
    Mar 22 19:32:00 host last message repeated 1 time

This created a core file on a directory name server files exist,
when it occured.

I wonder if someone knows what is the meaning of this message 
and what is the cause of this occurrence.

Thanks for your help.