The initial setup of my new 101 XS went ok and I was able to connect through my Linksys Compact Wireless-G Broadband Router WRT54GC v2
using wpa2 protocol and a rather long shared key with mixed case letters and quite a few symbols. The tablet alerted that a firmware update was available and I allowed the update to run its course. As soon as the update to 4.1.2 (Android 4.1.1) was completed I noticed my router was not within reach (even though it was within 2 meter distance) when occasionally (after restarting the tablet) it was "within reach" (duh) it did not pass the verification and no connection was established. I was rather annoyed because only 30 minutes earlier I had downloaded the firmware update using the exact same credentials on the exact same router. Also infuriating was the fact that all routers in the neighborhood were visible including signal strength indications but the wifi router almost touching the tablet was not "within reach". There are plenty of discussion threads dealing with WifI problems after an Archos firmware update (with many hints that the Archos programmers/engineers should be pelted with donuts for producing erratic, seemingly unnecessary updates that instead of enhancing the functionality rather seem to cripple the tablets), but almost none of these discussions pointed me in the right direction. The first thing I did was to make the wpa2 password extremely simple and on one occasion it did connect successfully to the router, but after resetting the password (wpa2 shared key) with a more complicated one the problem returned and I was even unable to replicate my succes with the very simple password. Then I tried to connect to a different router, I happen to have a MyFi gadget (huawei mobile wifi), and things were not looking great, but after restarting the tablet it did manage to connect to this MyFi router without problems (which is excellent when I am on the road but too costly when I'm at home doing some serious downloading and file transferring). In one of the threads it was mentioned that the router could be the culprit, such an observation is counterintuitive when all was fine with the very same router
before the firmware upgrade.
However I'm a pragmatist and leave no stone unturned when dealing with "computer problems" (in other aspects of life I readily give up after the first hurdle but in the digital realm I am determined as an Olympian to see things through and go for gold). I assumed I had the highest FW for my WRT54GC Linksys router but it turned out that there was a more recent update. To end this already long story: after the update of the ROUTER I had no problems with connecting the tablet to the WiFi router (all WPA2 settings the same as before the tablet FW update). The moral of the story is (I suppose): when no WiFi connection after tablet FW update (= desperation ensues + urge to smash the tablet against the wall) try to connect through a different router (in order to eliminate the updated tablet as the source of the problem) if that is successful you may have to upgrade your primary router (i.e. the one you normally use but that all of a sudden refuses the tablet after the FW update) or possibly replace that one (maybe you can send the bill to Archos). It is a pity that the Archos FW programmers/engineers do not pay more attention to this problem which apparently is not uncommon, but I can also understand that a proposed upgrade cannot be tested on all the hundreds if not thousands brands of Wifi routers that are on the market.
PS: resetting the tablet after the FW update and then reconfiguring the tablet DID NOT work, tried that at least three times!