Where I notice it the most is at http://gusgus64.wordpress.com/ BUT it's entirely random. It even happens when I visit other sites sometimes. And it's a recent development, which was what had me thinking it was something other than the normal lag in loading.
I just tried to get one of my posts to do it, just to see if perhaps I wasn't waiting long enough for it to load, but of course (!!!) it wouldn't do it for me now.
I'll wait for it to appear randomly and then give it extra time to load and see what happens. What has worked in the meantime was to click on the image (the thumbnail size) and that would bring up the full size image in a new page and then I'd go back to the post and it would be OK.
Will let you know if I encounter it again and what happens if I show more patience.......
BTW... what a wonderful job description (happiness engineer!) :D