Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable) after Upgrade

[basti <mailinglist@unix-solution.de>]

Hello,

I have upgrade my debian samba domain controller yesterday.
After that I get on both (dc1 and dc2) this error:

Could not get lock /var/lib/apt/lists/lock - open (11: Resource
temporarily unavailable)

I have try to remove the look and list files, reconfigure all installed
packages but the error is still present. I have also try to reboot.

Any ideas how can I fix this?

Best Regards,
basti