I'm using latest Turnkey Core.

This should reproduce the error but maybe its how I do things:

• Did a fresh install
• SSH into virtual machine
• Run apt-get update
• Run apt-get upgrade, this produces the following error

Errors were encountered while processing:
 /var/cache/apt/archives/webmin-custom_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-file_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-firewall_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-net_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-useradmin_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-passwd_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-shell_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-software_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-sshd_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-syslog_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-time_1.430-turnkey+25+g9c9e27c_i386.deb
 /var/cache/apt/archives/webmin-updown_1.430-turnkey+25+g9c9e27c_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)