[CentOS] Top process automatically killed

Hi,
    Can modifications to /etc/security/limits.conf cause top process to 
be automatically killed.

First, Here is the contents of the /etc/security/limits.conf

*                hard    cpu             2
*                soft    nproc           5
*                hard    nproc           10
mailnull         hard    nproc           100


What i have noticed that top process is always killed, But after hacking 
investigations like monitoring bandwidth, monitoring chatbots, running 
rkhunter, verifying ps & top binaries i found the server appears clean.

During this monitoring i noticed that always top process automatically 
killed when TIME+ column shows 1:59.96 and not all top processes are 
killed at the same time (i am logging via multiple ssh sessions),just 
the process that get 1:59:96 in the TIME+ column.

Now, are there  anyway that i can -as root-  do that with myself by 
previous settings.

thanx for your concern.

hameed