Cubase 6- Audio plays before event start?

I have a problem I cannot get my head round. I’m editing a lead vocal and I noticed the audio was playing before the start of the event.
I assumed it was a double or send effect but having disabled/muted/bypassed/turned off/turned down everything, I’ve noticed that it’s the actual audio on the selected track and it is starting around 1/16th ahead of where it should actually start? So basically in an area with no audio it plays the audio that’s just about to come up.This is making it real tricky to do precise edits.
I checked some other projects and it seems to have the same problem for any track, I thought maybe it’s a problem with my interface settings for latency etc but not sure why it would be playing before the event instead of after if that was the case and changing those settings has no effect. I also thought it may be some plugin delay compensation that was going to far but even when stripped of any plugin the problem si still there.
Any ideas why this could be happening or what settings I could change to make sure the audio is lined up with the event start? I imagine it must be soem global setting but have no idea what.

Thanks and Merry Christmas.

I’m using Cubase 6.0.7 on an Imac, through a focusrite liquid saffire:
Model Name: iMac
Model Identifier: iMac11,1
Processor Name: Intel Core i5
Processor Speed: 2.66 GHz
Number Of Processors: 1
Total Number Of Cores: 4
L2 Cache (per core): 256 KB
L3 Cache: 8 MB
Memory: 4 GB
Processor Interconnect Speed: 4.8 GT/s

Just to follow up. I realised there was a bypassed compressor on the stereo out. Therefore think this could be related to plug in delay compensation. This leads to another question. If an effect is bypassed and not causing a delay, does cubase still compensate? This would explain why the audio starts before the event but it seems to not make sense to compensaye for an effect that is not in use. If anyone can clarify that would be fab!

When I removed this effect from the stereo out the amount of time the audio starts before the event is heavily reduced but it still starts before the start of the audio event?

Any suggestions