Maximum number of memory segments that Notes can support has been exceeded

I have this annoying problem on our primary mail server:
When server has been running for some days this message will be returned 
to everything tries to do.
"Maximum number of memory segments that Notes can support has been 
exceeded"
This happens for about an hour until it eventually crashes.
I scheduled a weekly restart of server, which avoided the problem, in the 
beginning, but now it is down to 5 days before it happens. 

I havent been able to find the cause of this. I am not sure if it is 
domino- or i5  configuration that needs adjustment.
Any advice would be appreciated.

Brief System info:
Domino 7.0.2 on i5 model 570 V5R4
3 domino lpars running
2000 mail files/users

Regards

Lasse Krogh Henriksen
MT Højgaard a/s

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