The only temporary solution I've found is right clicking 'user image' and viewing the image, then click 'back'... It doesn't fix it forever, but certainly long enough to do some RP posts >< )
I have this problem as well, thanks for the advice on how to temporarily fix it.
This only just started to happen to me, it's only on Firefox, which is up to date. All add-ons are up to date as well.
The whole adding something at the end of things would be great if it was just my own images acting up, but it's other peoples images as well. I can't very well go around asking everyone who's image I can't see to add something to their url.
Is it possible it is because of the Halloween bug? This thread was started around the Valentines event so maybe something happens to the cod during events?