Oh let me clarify a little further in my example above.

Let's say the correct image should be showing up as this:
www.domain.com/ubbthreads/userimages//1122.jpg

But instead we are seeing someone else's avatar:
www.domain.com/ubbthreads/userimages/225.jpg

All other avatars on the same thread are showing up correct, correct avatar with a double // in the image URL.

So only the incorrectly displaying avatar has a single / and is the wrong image.