I'm using a BT home hub and when surfing the WEB it seems to frequently crash a lot and I have to unplug it at the mains and restart it to get back on the web (did not have this problem with my old voyager modem) I have found out that If I go in the settings and DISABLE the HUBS built-in firewall everything is OK can any one tell me if I need to RUN a software firewall as well as the hardware firewall and if I'm compromising my security by turning it off.. -PS I'm using zone alarm Any help will be welcome Anna

Obviously the firewall shouldn't be MAKING the modem crash, so it might be worth checking whether any firmware updates are available. A firmware update will upgrade the software in the modem.
If you got the modem from an ISP you should check with them.

You aren't compromising your security by disabling the hardware firewall though when you have a software firewall in place. But there's nothing wrong in having both a hardware and software firewall between you and the big bad web.