trying to upgrade Netgear DGN2000 firmware on a Mac

[#1]

My netgear router has been falling over quite a bit recently - we've now got 2 Macbook Pros, 2 iPhones and an iPad which try to connect regularly.  There seems to be a problem with it assigning IP addresses as additional machines try to add on to the router which then needs a reboot to be able to get any of them on at all.  The Netgear website has upgrade files for this model, but when I download onto the Mac I get a message which says 'Mounting failed' on the file and then I'm not able to do anything with it.
I've done some googling and it looks like there is a known incompatibility issue with these netgear files and Macs.  So would I be able to download the file via windows onto a USB stick and then upload it onto the router via my mac or do I need to try an entirely different approach?  The router is not that old so I think it's still basically operating fine other than this.
Thanks.

[#2]

Instead of downloading the file as "DGN2000_V1.1.8.0.img", can you download it as something other than a .img file, eg - <SAVE AS> "DGN2000_V1.1.8.0.abc" - to avoid whatever unhelpful process is trying to perform an auto-mount, and then once downloaded try renaming the file back to "DGN2000_V1.1.8.0.img".

[#3]

Thanks for the answer.  I tried that and although I didn't get the 'Mounting failed' message any more, it still wasn't happy with the file.  In the end I did manage to get the file off a Windows machine and upload it from a USB stick via Firefox.  The router then refused to reboot but when I unplugged it and started it again, all seems to be fine, firmware upgraded done.
Two nights of my life I won't get back again tho 

[#4]

I'm glad to hear you got it working. 
Hopefully next time there is a firmware upgrade it should be easier to do, as I see from the release notes, that (item 3) adds "auto firmware upgrade" - whatever that is ! 
[quote=Netgear website]
DGN2000 Firmware Version 1.1.8.0
New Features & Bug Fixes
  1. Added Live Parental Control.
  2. Added WiFi Auto channel selection on power up
  3. Added auto firmware upgrade
  4. Added QoS
  5. Added support for Smart Wizard 3.1
  6. Fixed various WPS issues
  7. Fixed various DHCP issues
  8. Closed uPnP ports after uses
  9. Added capability to work with legacy devices by turning off WPS
  10. Now able to add multiple firewall rules
  11. Fixed GUI issue when making changes to PPPoE/PPPoA configuration
  12. Fixed various static route issues