Hi JA,
that's a familiar feeling! At times I really hate all this academic lark...But, some things I've found helpful - for me a central problem is feeling that I don't write 'good enough' text - so at problem times I give myself freedom to write poor text, just write down things I know already and want to say (rather than indepth text with hardcore scientific debate). I also think of my writing as drafts which I will rewrite in due time.
The same works with reading too - I try to 'fool myself' to browse through a book/article, or read it while eating, or even go to a pub to read (this can backfire though!) - often I end up getting inspired of it!
Also, I don't know what you are doing, but for me it helps to change from one topic to another - instead of lit review think of methodology etc
Well, there's my good ideas - and I should really try to get into work now myself... not doing too good today either :-/