Process ID does not correspond to an SDE server?

Hi all,

I am having some problems with ArcSDE at the moment, when i try the following syntax
I get the following message
There are no ArcSDE users logged in.

I have then looked in the SDE.PROCESS_INFORMATION table and can see the users who are logged, in but when I try to kill a user using the SDE_ID, i get the following message
Process ID does not correspond to an SDE server

The same thing happened last week and we restarted the database and SDE service and it fixed it, but the problem is back again.

We are using ArcSDE 9.2 (we are planning on upgrading next month)..

Has anyone got any ideas why this might be happening?

Thanks