I'm trying to flash my N900. A few days ago, when I tried to switch it "on" in the morning, it behaved strangely. The power button does not seem to do anything at this point - so I removed the battery.
Now, when I insert the battery (well charged) into the N900, a white screen with large blue letters “NOKIA” appears. When I press “u” and insert the USB cable, nothing changes.
When I press the power button, and THEN insert the battery, the notification light comes on briefly (blue), and again a white screen with large blue letters “NOKIA” appears.
When I insert the USB cable first, and then insert the battery, a white screen with large blue letters “NOKIA” appears and the USB symbol appears BRIEFLY in the right top corner, and then disappears. After a while, the screen dims with the word “NOKIA” still faintly visible. There is no USB symbol. The notification light flashes as though the battery is charging.
I seem to be unable to switch the phone “off” other than by removing the battery.
It appears the USB connection between the phone and the PC can not be established.
I think I have all necessary files – before the phone started its current behavior, I could connect to the Nokia Suite just fine.

Any help? Any suggestions?

Your USB connector is damaged. I have successfully flashed through a damaged USB connector, but it is difficult and not guaranteed to work. Give it a shot a few times with the cable exerting pressure from different angles on the N900 usb connector.

Otherwise, time to shop for a new N900!

I'm afraid it is not as simple as that - re-read my OP

Not really - the N900 used to be may main (only) phone - now it was just a spare since I got my LG Android.