Thanks to the comment by Annie I – once again – looked into the grid view matter. Unfortunately the Sight theme has only received one update (1.0.1) since its initial release in November 2010 and is somewhat outdated. It looks like WPShower is not active anymore (the forum is madly spammed and the last tweet is from late 2011).
So I have somewhat redone the grid-list-jquery and put it in a separate file. The script now checks if the cookies already exists (this is what caused the problem before, because the cookie was only set after the first page load). All the hover effects and the toggle are now working.
You can download the files here. Simply unpack the archive and overwrite these files in your /wp-contents/themes/ folder. (I have only added the files I made changes to.)