Comment 3 for bug 1309695

I have installed ubutu 14.04 beta which automatically reverted to 13.10 about two months ago.
My ditribution is 13.10.
Every time I run the upgrade to 14.04 it fails on the second step of the 14.04 upgrade
I tried to upgrade using the upgrade manager and the command do-release-upgrade

The following error shows up:

Could not calculate the upgrade
An unresolvable problem occurred while calculating the upgrade.

Along withe following message:
This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

Help, SOS