Philips SN6500 router firewall problem

I am having trouble with the built in firewall for the Philips SN6500 Wireless Router.

Enabling the built in firewall prevents webpage images from loading. All I can see is the image placeholder. Disabling the firewall fixes this problem.

I am also running Online Armor firewall but disabling this makes no difference.

Is the routers firewall necessary or is Online Armor adequate?

If anyone has a solution it would be greatly appreciated as I would like to be secure as possible.

Thanks in advance.