asterisk users - Jan 2009 - Asterisk CLI got freezed!!

Hi All,
I am using asterisk 1.4.21  with iaxmodem and  hylafax which is sending fax
from my system with zap device.
I am facing a problem that some times my asterisk CLI got freeze and i am
not able to get any information from asterisk.
I need to restart the asterisk compulsory to work it again.
And because of this my iaxmodems are also getting time out from asterisk.

Please provide some help regarding this freeze issue.

Thanks,
Max Alex
Voip Developer
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Make sure the DNS servers Asterisk is using are not becoming
unresponsive or unreachable. Asterisk blocks on DNS requests so if it
doesn't get a response it will appear frozen.

Regards,

Greyman.