7960 unable to upgrade or downgrade

[jeckert]

I have a 7960 from a CCME install with version P00307020200 on it unfortunately this version would seem to have a bug with ccme and shared lines where the phone keeps ringing but no line is. I have found this does not occur on P00305000600 however of the 2 7960 phones at the site only one would downgrade. The other gets "Version Error". I can't upgrade either. same error.

[b.hsu]

Version 5.x and later images accept only signed binary files, which improves security on the Cisco IP Phone 7960 and 7940. The use of signed binary files does not allow you to return to an earlier software version. Once a Version 5.0 firmware image is installed, for instance, regardless of protocol, it cannot be replaced with any previous version.

http://www.cisco.com/en/US/products/sw/voicesw/ps4967/products_upgrade_guides09186a008022a968.html#wp1046332

You can downgrade to any other signed image

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