DDJ-RB - Headphone Delay

I recently bought a DDJ-RB and I'm getting this strange but extremely frustrating problem where the music coming through the headphones on cue is slightly ahead/behind (I can't quite tell) of the music coming through the main mix on the speakers.

This is of course making it impossible to mix!

Things I've tried so far:

1. Reinstalling both the rekordbox software and ddj driver2.

2. Trying basically every combination of setting in the audio settings tab that I can think of.

3. Downloading the latest DDJ-RB driver manually off the website and installing that just in case

4. Also doing the same with the firmware download on the website

My audio controller is a Tascam US-122L. I have the sound going through my computer as I use active Yamaha monitors coming from the Tascam so no other RCA inputs to plug the DDJ into. I've played with the latency settings on the Tascam too.

However the delay seems way too much to be the usual 2-10ms I might get with audio hardware. To me it sounds like 0.1-0.2 seconds - we're talking almost half a beat.

I'm on windows 8.1 64bit.

Doubt it should matter at all but the headphones are KRK 8400s.

I've tried working out a solution by having my headphones come from the Tascam but when I do that it cuts audio from the speakers automatically.

I have posted pictures of my settings and any computer information I could find.

Please help because it seems like a great product apart from this one issue but this one issue is making it completely useless!

Edit: Oh yeah one other weird thing for me is that the latency slider is always greyed out and i cant move it (but i can change latency settings in the setting utility). I just haven't noticed this on other post on the forum.