My Avatar was re-set?!?

Definitely because it's racy!

It's possible that the admin has gotten some messages complaining about your avatar because it's offensive to some people. I highly doubt you are the first person to have this happen to you and won't be the last. Do yourself a favor and find something a little less provocative to promote yourself with.

If they didn't send you a warning or anything it may have just been an oops or computer glitch. If you sign back in and it is gone again I wouldn't put it back up. But it's up to you.

the reason they probably changed it back is because they dont like the picture that is on it because it is not approprait for there site so becareful you might make them mad and get the boot

If your avatar does not follow the guidelines of the site I guess the admin or moderators will reset it to default. Its just an assumptions though, Im not really sure about it.

Probably because it is racy. You should change it back because they're just gonna change it when they see it anyways.