I think i was able to reproduce (or semi-reproduce) the problem. After messing up for some time with loading and reloading drivers via selector applet, sudden of nothing I'm not able anymore to connect into my network. Steps are exactly like pierrem reported, with exception that after some time of wifi-status icon flashing, I got message:

"Error connection to Internet: could not receive IP address from server. Try again?" (I get communicate in my language, so translation may be not accurate to the letter - of course trying again don't help)

From that point, nor bleeding edge or stock drivers are able to connect me.

dmesg print output as usual, stating that i was authenticated with AP - so it's likely really part with negotiating IP from DHCP that fail.

Strange thing is that other computers in my network doesn't have this issue, and if i reboot N900, initial connection to Wifi work. Ho ever, if i use applet to disable and enable wifi, I'm not able to connect anymore. What on earth?

I'll check if wifi-switcher work (uinstaled it already), and update my findings soon.

Anyway, could it be that way selector applet unload and load drivers screw something badly with configuration? I double checked settings and disabled/enabled again auto obtaining IP from dhcp. Will check if static IP work.

The most FRUSTRATING part is that i have absolutely no idea what i did to "trigger" this error, and now I'm unable to get rid of it Prior to that point, i was using selector applet to enable and disable my wifi quite often, sometimes even load bleeding edge - without ANY troubles. for worst-case scenario i got backup, but I'm really curious to find source of problems...

// Edit 1
Reinstalling selector applet doesn't help. I checked from my router side, and its true that my N900 is "connected" - can see client and signal quality via tomato firmware, ho ever IP is not obtained. the strange thing is that MAC reported to router is different than my usual N900 MAC? I got static dhcp rule that always worked, now i see that connection attempt is made with totally different MAC. Still, I'm sure that it's me trying to connect. and keep in mind that we're talking about stock drivers attempts.

I wonder if that can be a clue to our problem - anyway, keep in mind that i DON'T have MAC filter set on my router, so it can't be direct source of problems. Will investigate further.

// Edit 2

Just small update - at every attempt to connect again via prompt asking me if i want to try again, MAC reported to router is the same. ho ever, if i shut down wifi via selector, and re-enable it again, mac changes to another fresh one. Also, first 3 portions of max adress (parts between ":" ) are the same, only last 3 parts are different.

IDK if this is normal behaviour for wifi connection in stage of negotiating IP address (or any post-wpa2 authentication), so this may be totally irrelevant info. If so, correct me.

With bleeding edge drivers situation is the same - constant N900 MAC reported to router when i re-apply attempts to connect, but switching drivers on and off result in MAC that have 3 last portions different. Still don't know if this info is valuable, i hope so...