Problems installing HP Color LaserJet 5550 on Airport network

Question

I've been trying to install my dad's HP CLJ 5550 on our home network for ages.
*This is some background story, skip to the last bit if you don’t feel like reading*
Some months ago, everything was fine and dandy. We had a network consisting of:
The modem from our ISP
The switch from our ISP (I think that's what it was)
1 Airport Express 802.11n
2 Airport Express 802.11b/g
The 802.11n AE was connected to the ISP switch with a standard CAT5 ethernet cable, and that was in turn connected to the modem, and was transmitting the signal to the two other AE's, one connected to our printer with an ethernet cable, the other connected to our home stereo for AirTunes.
Then came the day when our ISP sent us a new modem, this time a wireless router/modem hybrid.
I got rid of the switch and modem and replaced them with the upgrade.
Furthermore, the new ISP router had WiFi built-in so naturally I wanted to take advantage of that, but in the end we ended up having 2 seperate networks, one transmitted by the ISP router and one transmitted by the 802.11n AE (which is connected to the ISP router w/ ethernet cable) to the other AE's.
The ISP router network had great internet performance whatsoever, but I couldn't get the printer and AirTunes working.
The AE network had very shaky internet performance but the network seemed very stable and served AirTunes and wireless printing.
After some time I tried merging the 2 networks, by setting the AEs to join the current network that the ISP router was transmitting. It kinda worked, but we lost all printing.
The printer is crucial to my dad so I suggested getting an AEBS so he bought that.
*SKIP TO HERE*
Now I've set the network up and it consists of:
1 AEBS (802.11n)
1 AE connected to the printer with an ethernet cable.
2 AEs connected to 2 different stereos.
1 ISP router (but this time I've disabled the WiFi!)
The AEBS creates the network, gets its internet connection from the ISP router, and is extended by the 3 AEs. Very fast, stable and AirTunes performs great... But the printer.
I’ve set the printer to TCP/IP and manual config.
The IP adress I’ve set to 192.168.1.150 (in line with the rest of the network)
Subnet mask is set to 255.255.255.0 since that’s what Airport Utility says.
Gateway Adress is set to 192.168.1.1 which I guess is the ISP router? I don’t know. It’s just what Airport Util says. Should it be the AEBS’s adress?
Are there things that I need to disable on printer? On the network? On my computer? Enable? Something? Aaaaargh..
I get nothing from pinging the IP-adress. Back in the golden days it used to recognize it as an HP printer it even checked ink levels and so forth.. Now I can’t even ping.
I’ve tried changing every parameter I can think of.. Adding it as LPD, IPP and HP JetDirect Socket.. (but since I can’t even ping what would I get from changing that?)
That turned out a wee bit longer than I expected...

Answer 1

The Firewalls are disabled and from my laptop you can view all of the shared
Folders on the Desktop with the CP1215 attached via USB.
When I issue the print from my laptop that is on the same network, you see the
print file show up in the CP1215 print queue of the Desktop the CP1215
is USB attached to and then disappears about 15 seconds later.  Here is
how it appears on in the Desktop CP1215 Print Queue before it disappears
Doc Name            Status      Owner     Pages    Size            Submitted            Port
E-mail print           Printing      Guest          1      547 KB     2:00pm 08/26/09      USB003
I've also download/installed the latest drivers.  When I reinstall the CP1215 on my laptop from
the Desktop, the "PRINT TEST PAGE works from the Laptop but then all print commands after
that do not work.
I see from my Google search I'm not the only one having this problem
ANY IDEAS what to try next? 
Wes