If I have my N900 powered off with no battery inserted (no power at all, battery out of phone for more than 10s) and nothing connected to the USB port and then insert the battery the phone displays the Nokia logo for about 5 seconds (with the screen being in that very dim almost unreadable state) then the screen goes blank and the status LED goes bright yellow then fades out.

If I then press down on the power button, the exact same thing repeats itself (nokia logo on very dim screen, yellow status LED)

However, if I plug the phone into either my wall-wart charger or my PC USB cable (regardless of whether I have the cable plugged in first or the battery in the phone first), the phone then boots into act-dead mode (which is exactly what it should be doing when its powered up with cable plugged in).

It seems like somehow the hardware (or BME or something) thinks there is a phantom USB cable plugged in when there is most definatly no cable plugged in (which causes the phone to start up in the wrong mode) but then it find it cant get any juice from the charger it thinks is plugged in so it kills the phone (hence the yellow status LED).

I am 100% certain its not a low, flat or faulty battery causing this to happen (I have tried multiple batteries both of which are confirmed "good" and at least one of which should have plenty of juice left in it)

I am not running the BME replacements or any modified kernel so those cant be causing this.

I dont see anything strange in syslog when I boot the phone with the charger/USB cable plugged in and I dont even know if the hernel (much less syslogd/klogd) are starting up when I power it up with no cable (and it does the "nokia logo then yellow LED then off" thing)

Does anyone have any ideas what I can try, I really need to get my phone working again to the point where it boots with no cable/charger plugged in...

I dont know why but after leaving the phone plugged in to the wall wart for a long time, I heard the usual "charger sound" and as of now it appears as though my phone is back to normal I hope.

Sounds like an empty battery after all.

Looks like my phone is somehow screwed up.
I have nothing plugged into USB at all yet cat /sys/devices/platform/musb_hdrc/charger shows 1 so it thinks there is a charger plugged in.

Seems that whatever hardware device or component detects the presence of something plugged into the USB port is somehow telling the kernel (and nolo) that there is something plugged into the USB port when there is not.

So I have a problem where when I boot the phone with no cable, nolo acts like there is a cable plugged in, tries to do what it normally does when cable is plugged in but cant (because there is actually no cable so the other part that pulls power from the USB power pins says "hey, no power here" and makes nolo shut down)

Then if I do boot the system (with either the Nokia charger or the Nokia PC cable connected) it boots into actdead mode and proceeds to charge the battery.

Tried reflashing and that didn't help.
It cant be a dead battery since I have charged it to full (where the LED went green and all the indicators said the battery was 100% full), disconnected the power cable, powered off the phone then tried to power it back on again where it had the same "wont power up" symptoms.

I hope to god my precious N900 doesn't have a hardware failure otherwise I am in deep trouble (if my N900 wont work, I will have to buy a new phone and I seriously doubt I can find another N900 here in Australia at a price I can afford)

Well, the presence of a charger is detected by the USB data pins connected together. If you have some fluff stuck in your USB connector that shortens those pins then that might have a similar effect. However you say you flashed the phone which requires the data pins working so that explanation seems unlikely. I guess it would not hurt to try taking a thin needle or something and cleaning the USB port but with no guarantee of a success.

hardware problem trival to repair if you know what you are doing .
For me i would start with some flux on the usb port and heat it with a hot air gun ment to repair such stuff it usually goes like that sometimes a replacement is needed too .

or else you will need a multimeter to find out whats wrong
first thing to do is check the battrey terminals and i think you wont even need to open the phone to check whats wrong but reparing n900s is terrible job .
for now i only have one and it feels bad that my usb acts up too

though my port was solid it is hostmode that destroyed i was like crazy plugging all kinds of usb stuff i could find and i am amazed what the n900 can handle and the most intresting pratical thing done was a usb lamp plugged directly onto the n900 providing light hundred times better than the flashlight and yes its awsome doing macro video with it.

i ll probably open up mine pretty soon
also i got a spare board with a ripped usb that vivrates and lights up as the battrey is put in i ll see if i can find out why.

can anybody tell me a usecase for the board or rather how to use bluetooth or wifi or cellular
available parts
mainboard
display module
battries

current condition---
ripped bad condition port
starts up as a battrey is plugged in
stays at nokia logo

i can probably repair it but what it would be good for ?

''the phone
displays the Nokia logo for about 5 seconds (with the screen being
in that very dim almost unreadable state ''

my friend i believe its time your xtraclear screenproctectors be replaced
I changed mine and it felt like i upgraded the display

if applicable.

''in camera app when a photo is taken it says memory full unable to save content''
what is it ? as i was doing fine with an sd card it could save photos
i tried unmounting and fsck
backupmenu fsck
format mmc

When it comes to investigating/fixing the hardware, I dont own any electronic tools whatsoever (no soldering iron, no multmeter, no hot air gun, not even screwdrivers that will fit the special screws on the N900)

What about a needle? I'm sure that if not you, then your wife/girlfriend/mother/daughter (delete as applicable) will have one.