asterisk users - Sep 2006 - experience with phones locking up uniden and cisco

I am using the latest asterisk 1.2.12 etc...

I have uniden UIP-200 phones, Cisco 7960 phones, Cisco 7912 phones, 
Cisco 7940 phones.

It seems like once in a great while (perhaps every other month)
All of these phones lock up and have to be rebooted.
Are others experiencing this?

The UIP-200 has the latest version.
The Cisco phones are a couple version back, but its difficult to get the 
versions from cisco.
The phones are not even in use when they lock up.

Whats others experience.

Jerry