I can't even get it to boot. It just restarts after about 3 seconds when the main desktop appears. Please help!!!! I bought it just a couple of days ago...

What applications did yo install since you got your N900?

What files did you change in the file system?

Try reflashing it.

I don't know exactly how many apps i had. I just know that it started to restart constantly when i added a widget. I've added widgets before, but this never happened. How can i reflash it? I saw a clip on youtube, but it's too dark.

I managed to get my n900 into a reboot loop last week after installing the tweak app (forgot what its called) that allows you to change the grid snap for lining up desktop icons among other things. Anyway, right after I installed it, I began re-arranging the shortcuts/widgets on my desktop. I was trying to place the Media Player widget right beneath the status bar, and somehow the widget jumped ON TOP of the status bar and forced the device to shutdown/reboot. Whenever the desktop started to reload after booting up, the Media Player widget would try to load at its last known location, right on top of the status bar....reboot...reboot...reboot. I just followed the instructions at http://wiki.maemo.org/Updating_the_firmware
to reflash and now all is well.

I'm gonna do it now. Thanks.

Mine just went into a persistent reboot loop. Happened when I turned on my bluetooth headset. I took the battery out and when I put it back in, it immediately started rebooting over and over again. I took the battery out and connected the phone with no battery to computer with usb. Got one green blink fro the LED. Then I put the battery in. This time it didn't automatically come on and when I turned it on it booted right up as normal. Don't know how or why, but I wanted to share my experience.

I guess by connecting the usb it could have prevented it from mounting the other partition during the boot process, but I don't see what difference that would make.

Some days ago I installed tweego and copied some mp3 files to the memory card from my PC (using the n900 as a mass memory device).
Since then, I haven't used the phone other than for calling, but today I tried to play some music, and I realized that the music was not found. I tried to restart the phone and then it entered in a never-ending starting loop, having to take out the battery to stop it.
Since then, I have played around with the device, trying to find what the hell is going on.
- First I could start the phone opening the back cover, taking the sim out and connecting it with a USB cable to the PC. Then, the n900 started asking for language and configuration settings. Without entering anything, I switched off the phone.
- Disconnecting the cable I restarted again (no back cover, which does not mount the memory card), and no problem, old background and configuration, not asking for language, everything ok. Closing the back cover (which mounts the memory card) makes poping up the message "memory card corrupted".
- Trying to restart the phone with the memory and cover, goes again to the never-ending starting loop.

So, it seems to me that there is a problem with the memory card. It is the second time that this phone has problems with the hcsd. The first time I couldn't reformat it anymore, neither with the phone, nor with computer (PC or Linux), and I though that it was a hardware problem of the card. I bought another one and now it is happening the same. I don't know yet if the card is also "broken" but it would be the first time I hear that a device is able to damage a memory card to the extend that it can't be even reformatted.

Anyone having similar experiences?

If there is nothing important on your external memory card you might write zeros all over it , then apply a fresh partition table and create new partition(s) and filesystem(s) to it.
Did you always use the otions to safely remove the device from any PC???

Unfortunately there are lots of photos I would like to recover, that's why I haven't formatted the card yet. I will check tonight at home if I can recover something.
I would swear I always click on the safely remove device from the PC, that's why I'm wondering how cat this happen twice.