My 2850N froze up today, rebooted it and it came back on.

Now wifi doesn't work, no devices can attach to network, even though they see it ok

When I try and go into admin console using 192.168.1.1 from Mac I get teh logon page ok but when I login, it re-directss me to draytek.com homepage

Any ideas gratefully received

can not say what happened but if is not working correctly, try to reflash it
http://www.forum.draytek.co.uk/viewtopic.php?f=13&t=18763#p77799
just get the firmware for the 2850 so not confuse with the 2820

Can you reflash it without having access to admin console?

No don't need to have access from the remote page only the firmware tool controlled via a pc and the modem connected via cable
follow step by step

Get the Firmware Upgrade V.3.6.5 (Windows) tool from UK support (down of their page, guessing you have windows) ... unzip it

Latest firmware is 3.6.6 & use 232201 modem code, which is fine for most lines
ftp://ftp.draytek.com/Vigor2850/Firmware/v3.6.6/Vigor2850_v3.6.6_AnnexA/
Note you need to use the *rst* file and Not the *all*

follow this order to avoid time outs (have the upgrade tool ready and stand by first)

-Disable temporary firewall at pc
-use ethernet cable (modem to pc) & not via wifi
turn / switch off the 2850

-open the utility upgrade tool 3.6.5 (you have downloaded & unzipped)
- type at IP address 192.168.1.1 (unless you have changed it try the current one)
-load 3.6.6 the rst file(is recommended for your case)
-password the current one you log in
- leave there the upgrade tool open & stand by ...

While the 2850 is off ... press and hold (keep pressing) gently the small reset hall button ... turn on the modem while the reset button is still under gently press ... and while the leds starts flashing ... let go the small reset button ... and press the send button at the upgrade tool before the leds at modem stops flashing fast
Do not disturb until finish after couple of minutes

If any problem come back before gets permanent damage