Different thumbnail

I try posting an image, then when I see my post in the thread the thumbnail is something completely different, often an image I've never seen before.
I delete the post right away, so I don't know if the full image itself is different also, but I'll check next time it happens.
This has happened to me more than once today. What gives?

the server detected you are a faggot

>>1
Try clearing your browser's cache, reset your router, (if you use one) command prompt --> ipconfig /release ipconfig /renew, etc. See if that helps.

It happened to me again. And I clicked on the image, and the full image was the same as the thumbnail. And it was a Suicide Girls pic, and I never download Suicide Girls pics, so it couldn't have come from me. The file name in the post was of the pic I was supposed to have posted, though.
My friend is telling me it's a bug that happens when two people post at exactly the same time. Is there a way to prevent this from happening?

Posting at the very same time (down to the nano second!) is rare, but it did happen to me once! This happening to you multiply times seems unlikely, are you posting on /b/?

>>5
Back to /lounge/, please.