I tried an upgrade via the web interface, that doesn't work (it pretends to work, reboots & stays on the same firmware).

What is a "long reset"? I have tried the power off unit, hold down reset button, keep it held, power on unit, release reset button 5 seconds later (have tried waiting longer than 5 seconds - up to about 60 seconds)

Sadly when I do that the unit stops responding to me on LAN2 - it won't respond to a ping on 192.168.1.1 and the web interface doesn't open.

However if I boot the unit normally, then it happily responds via WAN2 on 192.168.1.1. I've given my PC a static address (192.168.1.100, as per the unlocking guide), it seems like the HG612 is getting its knickers in a twist when I try and get it to firmware upgrade mode...

Many thanks,
Matt

Found a long reset is power on, wait for unit to initialise and then hold down reset for 10seconds. That seems to cause a reset, but, when I try the "reset for 5 seconds" on power up in order to get into the firmware flash mode, I still can't connect. pings look like this:

Reply from 192.168.1.100: Destination host unreachable.
Reply from 192.168.1.100: Destination host unreachable.
Reply from 192.168.1.100: Destination host unreachable.
Reply from 192.168.1.100: Destination host unreachable.
Request timed out.
Reply from 192.168.1.100: Destination host unreachable.
Reply from 192.168.1.100: Destination host unreachable.
Request timed out.
Reply from 192.168.1.100: Destination host unreachable.
Reply from 192.168.1.100: Destination host unreachable.
Request timed out.
Reply from 192.168.1.100: Destination host unreachable.
Reply from 192.168.1.100: Destination host unreachable.
Reply from 192.168.1.100: Destination host unreachable.
Reply from 192.168.1.100: Destination host unreachable.

However, if I just boot the unit normally, it responds as expected:
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64
Reply from 192.168.1.1: bytes=32 time<1ms TTL=64

I have just tried dropping a 10/100 switch between my PC and the HG612 incase there was a speed negotiation issue, but that has no affect.

Feel like a right dork, it was firewall related - on my laptop ESET was blocking it, and on my desktop (what ever comes with win 8). Both used to show the same odd combination of some timeouts, but not a total block.

Not really sure why the LAN2 worked perfectly if the HG612 was booted normally, but the firewall then went all wonky when I booted it into firmware mode. Anyway the end goal was achieved and HG612 has now been upgraded.

Thanks everyone for your help.

Cheers

Not a dork, but "learn something new everyday"

and finally work have accepted that something is not working properly at their end.... only taken 6 months!

Probably be another 18 months before they fix it, but at least they are heading in the correct direction.