Mystery of the Disappearing icons.

Some of my icons have disappeared. I go to my user pics and there are blanks. There doesn't seem to be any rhyme or reason as to which ones. Yesterday one had gone, by today it is seven.

I know there have been icon problems in the past; but has this happened to anyone else recently, or is it just me?

ETA - it seems it certainly isn't just me - and cairistiona7 has pointed out that it is probably related to the maintenance on-going at the moment. So hopefully they'll just sneak back, looking a bit sheepish, later...