Since: Nov 27, 2007
firstly, in cubase, choose device setup from the menu bar along the top and choose,
VST connections, make sure in your output, it says stereo out.
in your project, where your tracks are, in the track inspector window, make sure it looks like this
this means mono in stereo out.
If you are using a stereo input in your VST Connections, then make sure you change the mono(above) to stereo. by clickin on it.
But mostly you should record in mono anyway.
what interface are you using? i guess check the obvious things like, leads and stuff, jiggle them about and make sure they arent dodgey if you already have done this stuff.