Cisco Firewall :: ASA 5505 Configuration For AT&T Microcell

We got an AT&T Microcell a couple of weeks ago, hooked it up to our CISCO PIX 506 firewall and it worked "out of the box". We then upgraded to a CISCO ASA 5505 when the Pix died last week. Got the ASA 5505 up and running pretty much "out of the box", only having to setup our IP addresses (inside & outside). The 5505 is NOT configured as DHCP since I have an existing server in house that assigns IP addresses and I don't want to mess around with changing everything. However the Microcell wasn't working on the new 5505. Found in the Microcell manual that the following had to be "open":

123/UDP (NTP)
443/TCP (HTTPS)
4500/UDP (IPSec NAT Traversal)
500/UDP (IPSec phase 1 prior to NAT detection)
 
From the 5505 Config Guide, I found that I needed to ENABLE NAT-T, so I did this with the following commands:
crypto isakmp enable outside
crypto isakmp nat-traversal 3600
 
Using the "Packet Tracer" in ASDM, I found that ALL 4 types of packets were allowed going from the ATT Microcell (192.168.10.52 on my INSIDE network) to the OUTSIDE interface (66.xxx.xx.xx). However, all 4 types of packets FAILED when the Packet Trace was reversed (Source = 66.xxx.xx.xx, Destination 192.168.10.52).
 
The Packet Trace pointed to the "implicit rule" to DENY IP traffic. So, using the ASDM, I setup Access Lists for the above 4 ports/protocols, both on the INSIDE & OUTSIDE interface, both INCOMING & OUTGOING. Still, no success and the Packet Trace in ASDM still pointed to the IMPLICIT DENY rule on either the INSIDE or OUTSIDE interface, depending on which Interface I was initiating the Packet Trace. I tried setting the Access Rules for "Any" IP Address (not just the public IP or the Microcell IP) on both the Source/Destination for all 4 ports. What is even more confounding is that when setting up these access lists to PERMIT traffic, my internal network  Internet traffic stopped for ALL workstations on my network. Phone started ringing no more than a minute after I applied any PERMIT rule. By deleting the rule just installed, traffic started flowing again.
 
My number one questin is why don't the access lists work and why does settin up a "permit rule" kill my internet traffic?
 
I'm not a network expert and sprinkle holy water on our network every morning. I cringe when I have to make changes (like putting in a new firewall) because I don't know all the inner workings, parameters and setups done over the years by predecessors. I need to get the ATT Microcell up and running and figure the experience will be beneficial as our next step is to setup a VPN.