Its ok, I managed to solve the problem. It was nothing more than an error on my behalf - I forgot to add some rules to deal with the Loopback address (127.0.0.1), so thats why Konqueror wouldnt start/was very slow to load.
So, if your writing your own custom firewall rules, remember: you need rules to deal with the loopback address - otherwise you end up with stupid problems like mine
Adding a rule, something along these lines, will solve the [dumb] problem described above:
# create a new chain called LOOPBACK
iptables -N LOOPBACK
# Allow ALL connections to the LOOPBACK addy (127.0.0.1) -- VERY IMPORTANT
iptables -A LOOPBACK --dst 127.0.0.1 -j ACCEPT