Just a heads up for everyone out there (and a plea for Draytek to check these kinds of issues out).

On upgrading my Vigor 2110Vn firmware to 3.3.5.1 (from 3.3.2, keeping the current settings), everything appeared to work OK, but the admin interface was then missing the Wireless LAN entry, so I had no way of accessing these settings. It appears that the wireless was actually still working with its original settings, just there was no way of getting to its configuration (and it didn't appear on the System Status page).

It looks like the problem was in the upgrade reading/interpreting the original settings. To fix it, I had to reset to factory defaults, which got me the wireless LAN entry back, and then re-configure everything. (I also tried restoring from previously saved config but that didn't work either; I didn't expect it to, since I guess that the .all upgrade does this process behind the scenes anyway.)

So just a warning to users. Don't rely on config. backup files to be able to save you across firmware revisions. (It's crude, but I keep screenshots of all the config pages with any extra notes on passwords, etc.)