That's already been solved: Link Removed
In short, WinRARs shell extensions are causing this.
In addition to the solution given in this thread, my advice is not to install WinRAR in the first place and to go for IZARC or 7Zip instead. (I'm using the latter and its shell extensions are working fine. You can't create rar-Archives, but what's that gonna be good for anyway? Rar being better than insert-compression-format-here is a myth nowadays.)