Understanding multiple image fetches in Firebug

I'm confused by firebug's output under the tab 'Net' > All:

I post this in the JS section, as I'm sure many js coders use firebug and my question pertains to firebug.

I have an image which appears several times on my site - the same image each time, just displayed in different places.

For each time the image is displayed, I see a separate call to fetch it from the server, with info on 'Queuing, waiting for response, receiving data' etc, all with the number of milliseconds shown.

It looks like it's being downloaded multiple times rather than only once.
Why would this happen, if indeed that is what that means?

Thanks

when this request is first been run the time should be greater than the next, because it shud be retrieving it from the cache. but it shud still show a time just less that the initial one.

OK, thanks for confirming that I should indeed be seeing multiple entries for repeated use of the same image.

However, they are all taking roughly the same amount of time to download.
It's a very large image, so we're talking about 3 seconds-ish.

Each repeation is also 3 seconds-ish.

Mmm, strange.
I'm at a loss as to how to debug this. What could I try?
Is there other info in firebug that I can't find / am not aware of, that would tell me more?

Thanks again