Been trying to figure this one out.. as usual its probably something stupid that I missed

Here's what happens:
--------------------
#apt-get install package_a
Reading package lists... Done
Building dependency tree... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.

Since you only requested a single operation it is extremely likely that
the package is simply not installable and a bug report against
that package should be filed.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
package_a: Depends: package_b but it is not going to be installed
E: Broken packages
---------------------------------------------------------
#apt-get install package_b
Reading package lists... Done
Building dependency tree... Done
The following extra packages will be installed:

libhtml-parser-perl libhtml-tagset-perl libhtml-tree-perl libio-socket-ssl-perl libmail-sendmail-perl libnet-snmp-perl libnet-ssleay-perl liburi-perl
libwww-perl

Suggested packages:
libcrypt-des-perl libdigest-hmac-perl libdigest-sha1-perl libio-socket-inet6-perl

Recommended packages:
libmailtools-perl libhtml-format-perl libcompress-zlib-perl

The following NEW packages will be installed:
libhtml-parser-perl libhtml-tagset-perl libhtml-tree-perl libio-socket-ssl-perl libmail-sendmail-perl libnet-snmp-perl libnet-ssleay-perl liburi-perl
libwww-perl package_b
0 upgraded, 10 newly installed, 0 to remove and 34 not upgraded.
Need to get 1188kB of archives.
After unpacking 3990kB of additional disk space will be used.
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
package_b
Install these packages without verification [y/N]? y
Get:1 Index of etch/contrib package_b 1.2-0.5 [35.3kB]
Get:2 Index of / etch/main libhtml-tagset-perl 3.10-2 [13.7kB]
Get:3 Index of / etch/main liburi-perl 1.35-2 [87.8kB]
Get:4 Index of / etch/main libhtml-parser-perl 3.55-1 [108kB]
Get:5 Index of / etch/main libhtml-tree-perl 3.19.01-2 [208kB]
Get:6 Index of / etch/main libnet-ssleay-perl 1.30-1 [192kB]
Get:7 Index of / etch/main libio-socket-ssl-perl 1.01-1 [42.8kB]
Get:8 Index of / etch/main libmail-sendmail-perl 0.79-4 [27.6kB]
Get:9 Index of / etch/main libnet-snmp-perl 5.2.0-1 [112kB]
Get:10 Index of / etch/main libwww-perl 5.805-1 [361kB]
Fetched 1188kB in 2s (403kB/s)
Selecting previously deselected package libhtml-tagset-perl.
(Reading database ... 27638 files and directories currently installed.)
Unpacking libhtml-tagset-perl (from .../libhtml-tagset-perl_3.10-2_all.deb) ...
Selecting previously deselected package liburi-perl.
Unpacking liburi-perl (from .../liburi-perl_1.35-2_all.deb) ...
Selecting previously deselected package libhtml-parser-perl.
Unpacking libhtml-parser-perl (from .../libhtml-parser-perl_3.55-1_i386.deb) ...
Selecting previously deselected package libhtml-tree-perl.
Unpacking libhtml-tree-perl (from .../libhtml-tree-perl_3.19.01-2_all.deb) ...
Selecting previously deselected package libnet-ssleay-perl.
Unpacking libnet-ssleay-perl (from .../libnet-ssleay-perl_1.30-1_i386.deb) ...
Selecting previously deselected package libio-socket-ssl-perl.
Unpacking libio-socket-ssl-perl (from .../libio-socket-ssl-perl_1.01-1_all.deb) ...
Selecting previously deselected package libmail-sendmail-perl.
Unpacking libmail-sendmail-perl (from .../libmail-sendmail-perl_0.79-4_all.deb) ...
Selecting previously deselected package libnet-snmp-perl.
Unpacking libnet-snmp-perl (from .../libnet-snmp-perl_5.2.0-1_all.deb) ...
Selecting previously deselected package libwww-perl.
Unpacking libwww-perl (from .../libwww-perl_5.805-1_all.deb) ...
Selecting previously deselected package p1mon.
Unpacking package_b (from .../archives/package_b_1.2-0.5_all.deb) ...
Setting up libhtml-tagset-perl (3.10-2) ...
Setting up liburi-perl (1.35-2) ...
Setting up libhtml-parser-perl (3.55-1) ...
Setting up libhtml-tree-perl (3.19.01-2) ...
Setting up libnet-ssleay-perl (1.30-1) ...
Setting up libio-socket-ssl-perl (1.01-1) ...
Setting up libmail-sendmail-perl (0.79-4) ...
Setting up libnet-snmp-perl (5.2.0-1) ...
Setting up libwww-perl (5.805-1) ...
Setting up package_b (1.2-0.5) ...
-----------------------------------------------------

So as you can see package_b installs fine (except for the auth prompt) - so why is package_a saying package_b is broken?

These are custom packages, but I have seen this happen with trying to depend on postfix, for instance.

edit: apparently these forums doesnt like cleartext links such as from apt-get output, but the actual output is fine for that part of the install