i was transferring some files from my computer to n900 and when i finished and disconnected the phone i noticed that MyDocs name changed from (my name) to (n900) so i shut it down and took off the battery, when i opened it again MyDocs name now is BCM2048B0 Initilaization Configuration. but all my stuff are the same and inside MyDocs, what happened ? is that harmful ?
after some searches i found that its the bluetooth name, i didn't change it and i don't have bluetooth ear phones.

it seems to be doing no damage. Do applications that are connected to MyDocs work? There probably is a way to change it but I don't know how, so all I can suggest is back up your files just in case it decided to die on you, then you have a backup when you re-flash.

all working ok, i've renamed the bluetooth which is the MyDocs name too, i just don't know what caused that in 1st place

it just happens sometimes. no big deal. i kinda liked the more long confusing name.

I suspect it's the disk label and unused my maemo, quite why your computer renamed it based on the phone name is beyond me. It is possible to rename back with mlabel or once mounted but there is no point and that's just adding risk.