Minecraft – Why can’t Minecraft go full screen properly

I usually don't have this affect when installing mods like Optifine, however sometimes they just fail to completely install.

It's a longshot but perhaps utilising a texture pack will fix the problem.

Otherwise try reinstalling Minecraft and the mods - remove all files under .minecraft from %APPDATA%, just remember to copy over your saves. Once Minecraft has downloaded all the files it needs, re-install your mods.

It sounds like you don't have port forwarding set up properly on your router. Merely opening ports through your firewall isn't enough, you're router has to know where to send data coming through a particular port, thus port forwarding. The difference between opening a port in your firewall and port forwarding is this:

Opening port in firewall:

What this does is allow your computer to accept connections through which ever port you open. This would equate to opening a particular door or window to you house so that someone could get in.

Port Forwarding:

Port Forwarding is where you tell your router to route all the data coming in through a certain port to a particular IP on your local network (usually looks something like 192.168.1.xxx) This would equate more to giving someone the instructions to find your house as opposed to opening a door or window for them.

Both are necessary, the data has to know where you computer is on your network and have the door opened so that it can be received by your computer.

A Website you may find helpful is THIS.

That website has instructions on how to port forward for a wide range of diferent router makes and models.

Hope this helps you out!