Having some problems with my keyboard with Cubase.

I got it set up just fine about an hour ago, I was flicking through presets and the it kind of held the notes down like as if release was at 100% so I restarted Cubase and tried to set it up again, but this time when I press a key, I only hear the note about 5 seconds later and sometimes it stays on for a very long time.

I followed the manual to set it up in the MIDI device manager. The part I didn’t understand was the (activate MIDI channels) option. What is that for? Do I need to do something with it if I’m just loading up any synth and start playing.

I got it working by selecting reset in the Devices setup window, but I’ve no idea why.

What is the most straight forward way to set up Cubase to receive MIDI from a keyboard (Since It Doesn’t Seem To Be Plug And Play)?

Thanks.

MIDI cable from MIDI out of soundcard to MID in of keyboard.