Same error here:
Install these packages without verification [y/N]? y
Get:1
http://apt.saurik.com tangelo-3.7/main openssh 5.8p1-9 [419kB]
Get:2
http://www.ambertation.de ./downloads/PLEX/ com.plex.client-plugin 0.7.0 [787kB]
Get:3
http://apt.saurik.com tangelo-3.7/main cydia-sources 0-11 [700B]
Get:4
http://apt.saurik.com tangelo-3.7/main uikittools 1.1.0 [13.7kB]
Get:5
http://apt.saurik.com tangelo-3.7/main unzip 5.52-5 [149kB]
Get:6
http://apt.saurik.com tangelo-3.7/main wget 1.11-3 [139kB]
Get:7
http://apt.saurik.com tangelo-3.7/main zip 2.32-5 [98.8kB]
Get:8
http://nitosoft.com org.tomcool.smframework 0.7.2b-6 [286kB]
Get:9
http://apt.saurik.com tangelo-3.7/main berkeleydb 4.6.21-4 [666kB]
Fetched 2558kB in 38s (65.9kB/s)
Failed to fetch
http://www.ambertati...ation_0.7.0.deb Size mismatch
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
Apple-TV:~ root# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
berkeleydb com.plex.client-plugin cydia-sources openssh org.tomcool.smframework uikittools
unzip wget zip
9 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 787kB/2558kB of archives.
After this operation, 459kB of additional disk space will be used.
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
com.plex.client-plugin
Install these packages without verification [y/N]? y
Get:1
http://www.ambertation.de ./downloads/PLEX/ com.plex.client-plugin 0.7.0 [787kB]
Fetched 1B in 0s (2B/s)
Failed to fetch
http://www.ambertati...ation_0.7.0.deb Size mismatch
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
Apple-TV:~ root#