asterisk users - Mar 2010 - CLI not working properly - Asterisk Freez

Hello,

I am using Asterisk 1.4.21.2 in a Centos 4.8 with a kernel version
2.6.9-89.ELsmp. The processor type is Intel(R) Xeon(R) Quad Core CPU
E5410 @ 2.50GHz. with 4 GB of RAM

Sometimes, I get a strange behavior from asterisk: The CLI commands does not
work and Asterisk cannot receive calls. also i can't make any call,
The output of every CLI command is weird, for example making a stop
now does not work. A core show channels shows many channels but
frozen, etc etc

Please help me resolve this problem: what can be the cause of it? is it
Asterisk or my system? and what have I to do to eliminate this problem?

My solutios is either restart the server or kill the asterisk process
and restart it again

Thks in advance.
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