I needed to charge the N900 from my pc as travelling but was getting this message. I removed the battery and and tried plugging the usb in again but now it wont even turn on.
When the usb is plugged in, the yellow light comes on then after a few minutes the light starts flashing and the phone will vibrate and the nokia text will appear on screen but without back-lighting. its been going through this loop for half an hour now. Do you think my usb connection is broken?

I assume you are using a laptop.
Maybe those USB connections on your laptop do not provide enough power to charge the N900.

Even on some desktops I had to use the USB connections on the back of the PC to use with external HDD's because the front ones sucked.

I have exclusively been using this laptop to charge the N900 for the past week so it was working before.

Possible causes:

• cable broken and doesn't provide VCC
  try with another cable
• the usb port on the n900 comes loose
  try with the charger, if that fails too, get the device repaired.
• Mainboard on the laptop damaged (fuse blown?)
  try another device on the laptop port

I think that some USB connections balance on the knife's edge as far as providing power. A small thing happens, and suddenly they don't provide enough power. I have seen this message on USB connections that usually worked ok, and some physical change was needed to make them work again. I would assume that the message was accurate unless proven otherwise.

Check the power saving setting on the USB hub. I can't remember where they live (device manager? ctrl-panel > power options > plan settings? I think it varies with different flavours of windows).

Your power settings might be different from last week or there may have been some other USB activity that prevented the hub from powering down.

Or as geneven says there may just not be enough juice coming from the laptop. It'd be the simplest explanation!

Did you change or upgrade the driver for the N900 or any USB drivers?

I had the same issue, but when I put it in Mass Storage Mode instead of PC Suite (or not selecting either option), it started to charge right away. It wouldn't take a charge at all until I selected it. Only did this for 2 days and went back to normal. Strange, but give it a shot.

I have this message every now and then. And ussually when it happens, the phone does not connect correctly to the computer (In windows you get the message that the device was not properly installed).
I just unplug, and plug again, and it ussually works...

The USB in my phone feels pretty tight, and the cable is new. I think is more related on how you plug the cable (fast, slow, to the side, etc). sometimes the conection is not good.

Thanks for the replies, but it is in fact my computer which is at fault because it worked on a different laptop. I was uninstalling all the bloatware that came pre installed and its had some unintended consequences.