No Sound Panning Right [SOLVED]

Sonar X3 Producer 64 Bit. Win 10 64 Bit. Asus Z-87K Mobo. i5 4460 3.2(3.4 boost) GHz. 8GB DDR3 RAM. Akai EIE Pro.
 
Just recently I can no longer Pan my tracks towards right. When I do the volume decreases and the sound stays centred until it zeros (Volume, Meter still shows signal) at hard right.
 
When the Master Bus is set to interleave/mono, sound is heard through both speakers. When the Master is in Stereo, the sound is centred and when panned right decreases in volume. I am using the correct mono L/R inputs for tracks and the correct Driver for the Master lane. I've also applied each Panning Law within Sonar, but I get the same result. Note I am recording onto mono tracks here and these tracks are not paired. Another thing is that this also happens with a MIDI stereo tracks (in my case Addictive Drums), and previously recorded stereo tracks.
 
I have tried this with no other Busses present apart from Master to eliminate any conflicts. I also tested the stereo output of my audio interface from various sources and file types outside of Sonar, and it is working perfectly.
 
All my Drivers are up to date. I installed ASIO4ALL subsequent to this happening but the problem persists.
 
I hope this post is understandable, I don't know all the jargon and although I've been using Cakewalk (X1 ess'l, 2 Studio and 3 Producer) since May 2012, I'm new to these forums so I hope I haven't left anything out.

chuckebaby
stereo FX can sometimes cause problems like this.
Have you tried switching your speakers around (plug left in to right / right in to left) ?
I would eliminate FX until you can figure out the source of your issues.
 
Remember some FX, and even some synths, although they are mono tracks, run through a stereo effect, stereo synth.

Cheers for the reply. FX are not the cause. I checked that when I made a new Project with just two guitars and no FX or Plugins. Track 1: In= Akai In 1 Left, Out=Master. Track 2: In Akai In 2 Right, Out=Master. On Master I tried Akai Out 1 and 3 and also Stereo. All results were the same as in my OP. I'm perplexed as this only started happening yesterday. It effects all my other projects that were fine before. I haven't knowingly (famous last words) changed anything, but I haven't used  Sonar for a week prior to this issue.
 
I've uninstalled X3, and removed all the folders (backed up data to another drive to avoid file paths being detected on re-installation, in the hope a fresh install will reconfigure it (if I have messed with something) I also deleted all the H-Key Cakewalk associations in regedit.
 
Cheers again, I'll stay in touch with the results.