That's exceeded bandwidth. That's not a photobucket problem, but a user one. Aka; they uploaded too much
for a free account, which is like; 500 pictures +.
and i repeat myself, bandwith message isnt about the number of pics you have uploaded, but the times of views it gets. aka more views = more "downloads" = more bandwith spent

though for a free service both are nice. though for sigs and for images of one upload only i prefer imageshack, while photobucket is better for small images. the album comes handy for example, emots