Synchronized Folders have duplicate files ending in .wlx extension, why?

I have upgraded from 2011 to 2012 True Image Home recently on both my laptop and desktop. I synced 5 folders between the 2 PC's only, not with on-line storage.
4 of the folder, which have mainly documents and scripts are synced ok. The 5th is full of images, png, jpg etc. for every image file there is a duplicate ending in the wlx extension.
Is there a particular reason for this?
Will these files stay there permanently?

Also, I continually get notifications about the sync status, approx 2 a minute for the last 2 days.
Will these notifications continue forever while the sync is installed?