If you have granted yourself access privileges using the IP address form for the GRANT statement, the most likely problem is that you are trying to access a machine that is on the other side of a gateway which is translating your client machine IP address to something else.
According to my reading of the fine MySQL manual, if you specify an address form in the host table, it will check the source address of the connection for a match. Since that fails, it seems likely that, by the time the server sees the connection request, the IP address is no longer 192.168.0.3.
Your choices here are limited:
1. You can grant yourself privileges to connect from any host (%).
2. You can grant yourself privileges to connect from any machine behind the NAT by specifying the
apparent IP address that the server will see.
3. You can set up some sort of IP tunneling between your LAN and the network that the server is on,
so that your (tunneled) address is not changed.