Shareaza

When I click the "HOME" tab in shareaza, it says:-
Warning - You are Firewalled
shareaza has detected that you are behind a NAT router or firewall. ect.

However, the shareaza connection test says:-
Results
TCP: The TCP connection has been accepted by your computer and the request has been answered. This means that other clients from the networks can properly connect to you.
UDP: An answer has been received from your client! This means that Shareaza is able to receive UDP packets from the network.
Congratulations, everything seems to be fine and Shareaza should work properly.

I have set up my router according to port Forward, is the any chance my ISP may have firewalled me?
What else could the problem be, and how can I fix this?

The detection within Shareaza is not 100% accurate, due to the nature of this mechanism. The connection test is what you should trust.

Yes, for practical reasons most systems of automated firewall detection (including the one in Shareaza) use UDP packets and UDP packets can be delayed or dropped in transit by routers as convenient. So false positives are quite normal. Passing the connection test while behind a firewall OTOH is extremely unlikely. You can go to setting>connection and switch "Can accept incoming connections?" to "Yes", if you pass the connection test.