No issues here. Just downloaded 4 messages, each of which was over one and on-half minutes long. Do you have any issues downloading anything else from the internet? Can you download attachments from your emails? Just asking to see if this might be a computer or ISP issue.
I always recommend to my clients to reboot their computer to see if that clears up any lingering issues from other sources. Have you tried rebooting your computer and again try to download your messages?