This started this morning - about 1 in 10-15 times when I visit a full-image page, I'll see a list of the thumbnails in that same album pop up at the top of the Plogger wrapper like this:
I found something like that too. It didn't occur to me until I installed Nick's "Plugger". However, I found it to be a debug "echo" left in the code that spits out text filenames. Do a code search for "echo", and see if you can't find it.