The pdf ZD1100_961_MR_Upgrade.pdf contains a link to download the firmware but the linked page doesn't contain a download button only a link back to the original pdf.
Feeling a bit circular...
We've had reports of this before but we can't reproduce it here. Can you try with a different browser? We think it's related to some odd browser cache issue.
The problem originally appeared using Opera so I tried Firefox instead and flushed the history/cookies for good measure. Still no luck, I'm afraid. I've attached a screen dump in case it helps.