Okay now I've found something strange which i've never encountered before when reflashing. I list them in points so hopefully it will be easier to troubleshoot or debug (anyone...? ):

1) The regular way of reflashing (i.e. run flasher3.5 -blahblah on Windows/Linux => power off n900=>press "U"=>connect USB)
does not work after upgrading to kernel-power v44 (+ uboot).
I've reflashed my device many times before without any issue and I believe I am already familiar with the procedure.

2) When connected to the PC usb port, the weird thing is both windows and linux (debian under virtualbox) cannot recognise the device
- device manager (windows): reloads once but no device seems to be detected
- dmesg:
[ 121.812147] usb 1-1: new high speed USB device using ehci_hcd and address 2
[ 122.367779] usb 1-1: New USB device found, idVendor=0421, idProduct=0106
[ 122.367779] usb 1-1: New USB device strings: Mfr=34, Product=38, SerialNumber=0
[ 122.369731] usb 1-1: Product: Nokia USB ROM
[ 122.369731] usb 1-1: Manufacturer: Nokia
[ 122.384473] usb 1-1: configuration #1 chosen from 1 choice
[ 122.400697] usb 1-1: can't set config #1, error -32
[ 123.164786] usb 1-1: USB disconnect, address 2

there . This has never happened to me when doing reflashing before.

3) At first when the device reboot into uboot
the screen backlight is on,
but after leaving the device off for a whole night, there was no more backlight but a dim screen when powered up again.

4) I can still see the tiny-teeny words on the uboot screen. Here two things happened:
- if I just leave it running, boot stops at "Starting kernel" forever;
- if I press any key as per the uboot onscreen instruction, I get a prompt, but it's no bash (well of course...) or any regular shell so I don't know what commands I can use here. Is there any "help" file or things like for this build of uboot?

5) Charging seems to be working in my case, though, contrary to some other similar cases. The charging LED is on and the device feels a bit warm. But I don't know how to verify or measure charging in this situation.

Some questions and hunches:
1) It looks like the device is not actually bricked but simply gets stuck at uboot and cannot load the kernel(s) successfully.

2) It is not dead hardware-wise either as charging is still working.

3) As so far I haven't succeeded in reflashing the device, is it feasible to set up a multiple boot environment on the device and work around the problem?

4) Or is there any other way to rescue the system besides reflashing?

5) I was just installing everything from the ground up after messing up the rootfs and did not install backupmenu or make any backup, so how can I nuke the whole thing and start afresh?

Please don't tell me this is no return ...

PS I have tried the Meego rescue initrd before, well it worked for me to rescue things in emmc and MyDocs, but this tim e it fails to break into the device just like the failure to reflash...