Problem with security levels on router
 

Could someone please help me resolve a little problem I am having.

I wish to run a webserver off my pc, this is all fine, problem is that I can only do so on port 1025 upwards, which is a pain for A entries and makes assigning domain names hard, so they have to be a domain mask instead. When I port forward to port 80 it won't allow traffic in as I have to set level 1 security as pictured below, however when i try doing so my internet connection disconnects, and I cannot load any sites or open any internet related programs when its set to level 1, as soon as I reset the zyxel router to level 2 everything works again. The router is a "P643" Could anybody help resolve my issue?

Thanks in advance,

~ gazaa

Routers security levels:

http://homegrownforums.com/images/zyxtel.jpg