Why are my identical WLAN settings not recognised by my computers after reset?

Question

Recently I had to reset my Fonera 2.0 WLAN router. I reconfigured it immediately with the same private SSID, security mode (WPA2-PSK) and key. However, when I looked at my Windows notebooks, they were not automatically connected to the new/old network. Unfortunately I did not take a screenshot, but it showed a red symbol next to the SSID (with a red X). My WLAN printer and my Android phone lost their connection, too, and failed to regain it.

I was under the impression that identical settings on identical hardware should lead to identical results. I expected my network devices to recognize the new settings as the old and reconnect automatically.

An answer on Superuser (How can I get the same SSID for multiple access points?) states:

Many clients assume that these kinds of settings will be the same across all APs with the same SSID.

It further suggests to vary the channel between two APs. I did leave the channel selection before and after the reset on automatic, so this should have had no influence.

All my clients - printer, smartphone, notebooks - failed to recognise the network after reinstalling it with identical settings. Why was this the case? Could it be the router that sends a different signature or uses a different certificate after the reset (if something like that exists)?

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January 2012 edit:

Here's some more food for thought. After switching from my Fonera to a Zyxel 660 HN modem-router with identical WiFi settings most of my devices - Android smart phones, one Ubuntu netbook, an HP printer, an old notebook with a plain vanilla windows 7 - gladly accepted the new network without reconfiguration. A newer HP notebook with Windows 7 did not - though it has HP crapware installed that "manages" my network connections.

Answer 1

I was tempted to delete the question since I presume that I had something in the original configuration that I had not accounted for. Therefore the error was probably my own.

I've reached this conclusion after switching to a totally different router (Zyxel) where I re-entered exactly the same Wlan config as in the Fonera - same SSID and WPA2-PSK, though with a different channel - most of my devices accepted this switch without complaining. Except for a Windows 7 on a newer HP notebook. I get an error message about invalid credentials (or something like that - it's in German).

My plain vanilla Windows 7 made me re-select the type of network I was in (Home, Office, Public), but other than that it works fine with the new router.

To answer my original question: It appears that something was set in the initial configuration that I failed to transfer to the new settings after reset. And it also appears some clients - especially Windows - will not accept a "new" network with identical parameters like before if their internal IP address or the router's MAC address change.