A Microsoft file hosting and synchronization service.
I managed to narrow it down to OneDrive that was causing the issue. After reading Millewa's post I hunted down a way to delete the cache, and so far so good. Fingers crossed as this has been dragging out over a few days now.
I followed these steps to delete the cache (yes - I know its for SkyDrive but it still worked)
To clear your cache, close all your Office processes like groove.exe (which is SkyDrive Pro), msouc.exe, msosync.exe, office library sync,
Browse to “C:\Users%username%\AppData\Local\Microsoft\Office\Spw” and delete all the content. (You will see that this is all related to groove and spw = SharePoint Workspace).
Next, go to “C:\Users%username%\AppData\Local\Microsoft\Office\15.0\OfficeFileCache” and also delete all content from this folder. This is where all the caching from your files are stored.
After you deleted everything, you should be able to start SkyDrive Pro again (using “C:\Program Files\Microsoft Office\Office15\GROOVE.EXE“).
Good luck! I will re post if it starts playing up again :|