I think 'thesis avoidance syndrome' is fairly common.
My flat is cleaner than ever before - yesterday I urgently needed to dust the skirting boards, and couldn't possibly continue my write-up until all the skirting was shining!
There's always a worthwhile distraction. e.g. replying to random messages on this very forum.
I find the best thing is to reward myself with a sweet for every hour of hard work, but often i've scoffed the whole packet within 10mins. oh well, a good excuse to pop down to the shop...
good luck!