I believe you have to have the same kernel as the backup.
Have you updated KP since the backup?
Check the Backupmenu thread & wiki

Indeed, the backed up kernel version was different from the current one. So I took the opportunity to flash it with RX-51_2009SE_20.2010.36-2_PR_COMBINED_MR0_ARM.bin
Very sadly, the wifi still doesn't connect. I'm seriously annoyed now.

So are you back to a clean fresh PR1.3 and still no WiFi?

Yes. 2.6.28-omap1.
Do you think a complete flash with the eMMC help more?

Networks are detected, password requested when it's protected, even WifiEye showed them. Can we conclude it's not a hardware issue?

At least a full reflash will rule out stuff on the device, we need to work out if it's hardware or not.

I had nothing in wifi applcations with my problem.
check your dmesg now.
check your AP setting etc, and test on open network again.

dmesg is the same as before. It times out, whether I leave the network with no protection or with WPA.
I had enough of it for today. Will try a full flash tomorrow.

So tonight i fully flashed my N900, Vanilla and Fiasco.
As a result, I have a brand new machine, but still no wifi. The dmesg pattern is the same:
wl1251: down
wl1251: 151 tx blocks ...
wl1251: firmware booted (Rev 4.0.4.3.7)
wlan0: direct probe to ....
wlan0: direct probe to ....
wlan0: direct probe to .... timed out

So I guess I should conclude that my N900 has a dead Wifi.
Do you have any clue if I bring it to a shop (somewhere in Zürich), they'll know what to do with it?

Considered the time I'm spending fighting with it, I'm also good to buy another one, if anyone is selling his.

Thanks sixwheeledbeast for following.

jb

Anytime

Sorry about your dead wifi that sucks.
I can't think of anything else to suggest, after a complete reflash.
I can only say hardware failure. Which makes me a little worried that I had a similar issue.
Out of interest, have you ever overclocked it or had any other issues with anything?

No, never overclocked and no hardware issues.
The worst thing I had until now, was to use once the trick of plugging the charger cord while re-inserting the battery to unbrick it.

I took care of it, as I do with all my items (it had always a screen shield and the ugly rubber case), but since Dec. 2009 it lived well, saw many countries, experienced various tough conditions between -30°C and +45°C, felt some times on the ground, so what if it died at a normal age for a hero?

However, I now feel sad and lonely.

It's hard to compare with your case, as in mine, it's the first time (and seemingly last time) that it happened.

Actually, from time to time, I have (for Community Members) devices in very good condition, extensively tested to have every single part working (to last sensor), and USB port reinforced, as in forums guide.

Price and details are as were in this thread:
http://talk.maemo.org/showthread.php?t=84174

/Estel