Pbase used to do that all the time many many threads/years ago.
Something wacky would happen, and images would go weird and be seen one second and not the next.
No-one is sure exactly what happens.
Maybe their server needs to be defragged or something.
But it was a much more often occurence way back, and a point of humor/annoyance/anger in the DD before it became the Combined thread.
Are you sure it was Pbase and not Fotki? I don't think Pbase has been around too long like Fotki has. One of the reasons I went to Pbase was because Fotki was so unreliable.
Of course I'm old and half senile, so don't go too much by me.. ;)