apt-get -- Couldn't find package screen

did you do an apt-get update ?
It works on 6.2.0 beta3 with my RN104. I don't know the specifics for the ultra6.

What does your /etc/apt/sources.list look like?

Thank you for the responses.

This was the result of apt-get update:

nas-EB-01-0D:/# apt-get update
Get:1 http://www.readynas.com 4.2.27/ Release.gpg [490B]
Ign http://www.readynas.com 4.2.27/ Translation-en_US
Get:2 http://www.readynas.com 4.2.27/ Release [2752B]
Get:3 http://www.readynas.com 4.2.27/ Packages [64.4kB]
Fetched 67.7kB in 1s (51.6kB/s)
Reading package lists... Done


nas-EB-01-0D:/# apt-get install screen
Reading package lists... Done
Building dependency tree... Done
E: Couldn't find package screen

This is what /etc/apt/sources.list returned:

deb http://www.readynas.com/packages 4.2.27/

#deb http://archive.debian.org/debian etch main

What happens if you use vi to uncomment (remove the # from the start of the line) the last line in /etc/apt/sources.list then rerun the apt-get commands mentioned above?

Re-ran apt-get:

nas-EB-01-0D:/etc/apt# apt-get update
Hit http://www.readynas.com 4.2.27/ Release.gpg
Ign http://www.readynas.com 4.2.27/ Translation-en_US 
Get:1 http://archive.debian.org etch Release.gpg [1033B]
Ign http://archive.debian.org etch/main Translation-en_US
Hit http://www.readynas.com 4.2.27/ Release
Get:2 http://archive.debian.org etch Release [67.8kB]
Ign http://www.readynas.com 4.2.27/ Packages/DiffIndex
Hit http://www.readynas.com 4.2.27/ Packages       
Get:3 http://archive.debian.org etch/main Packages [4218kB]
Fetched 4287kB in 4s (914kB/s)     
Reading package lists... Done
nas-EB-01-0D:/etc/apt# apt-get install screen
Reading package lists... Done
Building dependency tree... Done
You might want to run `apt-get -f install' to correct these:
The following packages have unmet dependencies:
  libapache-mod-php5: Depends: php5-common (= 5.2.0-8+etch13) but 5.4.30-0rnx1 is to be installed
  php5-mcrypt: Depends: php5-common (= 5.2.0-8+etch13) but 5.4.30-0rnx1 is to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

Then ran 'apt-get -f install' with no packages:

nas-EB-01-0D:/etc/apt# apt-get -f install
Reading package lists... Done
Building dependency tree... Done
Correcting dependencies... Done
The following packages will be REMOVED:
  libapache-mod-php5 php5-mcrypt
0 upgraded, 0 newly installed, 2 to remove and 37 not upgraded.
2 not fully installed or removed.
After this operation, 5439kB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 18547 files and directories currently installed.)
Removing php5-mcrypt ...
Removing libapache-mod-php5 ...
Processing triggers for libapache2-mod-php5 ...
Your apache2 configuration is broken, so we're not restarting it for you.
Setting up php5-zendopcache (7.0.3-0rnx2) ...
ERROR: /etc/php5/mods-available/zendopcache.ini does not exist
dpkg: error processing php5-zendopcache (--configure):
 subprocess post-installation script returned error exit status 2
Errors were encountered while processing:
 php5-zendopcache
E: Sub-process /usr/bin/dpkg returned an error code (1)

Again, thank you for your earlier responses.

I was able to install screen once I uncommented the last line in /etc/apt/sources.list. However, when I try to run screen, it fails to open and returns the following error:

Cannot find terminfo entry for 'xterm-256color'

I am sure there is a simple fix but it eludes me. Is there a config file somewhere I can edit to fix this?

Perhaps try installing ncurses-base

Thank you. Apparently I already have the newest version

nas-EB-01-0D:~# apt-get install ncurses-base
Reading package lists... Done
Building dependency tree... Done
ncurses-base is already the newest version.

Also, I'm getting these annoying PHP5 errors.

The following packages have unmet dependencies:
  libapache-mod-php5: Depends: php5-common (= 5.2.0-8+etch13) but 5.4.30-0rnx1 is to be installed
  php5-mcrypt: Depends: php5-common (= 5.2.0-8+etch13) but 5.4.30-0rnx1 is to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

This does not appear to be interfering with the Newznab scripts though.

# export | grep xterm

You have a newer version of PHP installed from RNXtras compared with the ancient version in the apt-get repository.