SNMP appears to be broken in builds 3.3.7 onwards, still no sign of it been fixed.

I don't know if this is discussed in another thread (this is rather old)? Discussion in the Australian forum I mentioned a while ago continues actively:
http://forums.whirlpool.net.au/archive/1576557

There is a new version of the 2820 series firmware, 3.7.7.2 (7 June 2012)
Australians' preliminary opinions are favourable ("nothing seems broken (for me)") after huge problems with all earlier versions.
A typical comment:
"New firmware out, 3.3.7.2.

New Features
- None

Yay!"

ftp://ftp.draytek.com/Vigor2820/Firmware/

With all the reported problems haven't updated myself for quite a while.

HTH

I've just flashed it onto my 2820Vn via tftp (as my previous upgrade had failed and resulted in a "your router will die if rebooted" error message). Just the painful exercise of re-introducing all my custom settings.

It's been up and running for less than a day, so too early to determine reliability.

3.3.7.2 is still flawed.
I updated a router today from 3.3.5.2.
The router uses WAN1 as a backup ADSL line, and WAN2 as the main FTTC line.
NAT is used to map five public IP addresses to five internal servers so that they can be accessed externally.
Updating to 3.3.7.2 has killed the NAT on WAN2 - not only can the servers no longer be accessed externally, but they also lose access to the internet.
Failing over to WAN1 allows the servers to work properly again.
I've emailed support but suspect I will have to downgrade to an earlier version.
:evil:

I should add that the configuration is sound - I have set several clients up with this particular configuration. All that are still on 3.3.5.2 are working fine. I initially did a .all upgrade followed by a .rst and fresh configration, but still no joy.

i don't know if this has been reported in another thread.

For information (I haven't installed this), there is a new firmware version. From the release notes there are no new features, and just one bug fix;

Vigor 2820 series firmware:
v3.3.7.4, 12 April 2013

New Features
None.
Improvement
Corrected: PPTP log in possible with ??? and no password with activated LAN to LAN

ftp://ftp.draytek.com/Vigor2820/Firmware/v3.3.7.4/