I fixed a Bluetooth issue on the n900 by the following method (a bit of a combination of other posts & hopefully in layman's terms!)

A Warning - you need to be 'root' to do this (Administrator privileges), doing anything in root can kill your phone, if you follow this you won't break anything, if you muck about with anything else or any other file/folders you may kill your phone, and then you will need to wipe it and re-flash - not fun!

Also, by doing this, you will wipe any Bluetooth profiles/connections you have - you will need to re-connect with your devices again.

Open the X Terminal program

You should be in /home/user directory

You need to be 'root' to do this type:
sudo gainroot

You should now be root (super user) - to check, type: whoami - when you press enter, it should say 'root'

Now type the following:
cd /var/lib/blu*

You should now see and be in directory: /var/lib/bluetooth

Now type:
ls (That is LS in lowercase)

You should see at least 2 folders, one will be a MAC address which will look something like this: 08:00:69:02:01:FC And maybe a folder called 'maemo-callerid-allowed', and maybe some other folders. You are only interested in the MAC address, so now do this:

Now type:
cd 08*

NOTE: I put 08* as my MAC address example begins with 08, just replace that with what ever your MAC address directory shows as, the * just saves you having to type all the MAC address, as there is only one directory beginning with 08, you can put * for the system to do the rest

Now type:
ls (That is LS in lowercase)

You will now see the below folders

classes
config
did
eir
featured
lastseen
lastused
linkkeys
manufacturers
names
profiles
sdp
trusts

They are all to do with Bluetooth, you now need to rename each folder to the same name but with .old on the end, so if you ever need to, you can move it back, or access the old data within it - this will ensure you are backing up your data - there may be a quicker way in UNIX to do this on mass, but I am not a true geek (yet!)

Do this for each folder - and if you have any additional folders than I list above, do it for them also!

To change the name of each directory, type this:

mv classes classes.old [this changes the name of the classes directory to classes.old]
- Repeat this for every folder, example: mv config config.old etc until they are all changed

To check the status (if you think you have forgotten one) type:
ls (That is LS in lowercase) - This will list all the files and folders, if any are left just mv [original name] [original name.old]

Once all folders are renamed, the system will basically think it has no Bluetooth settings or information, and it should make all the folders again with clean brand new files in them with the default NokiaN900 name - to check this worked, turn the phone off, and back on, then go into Bluetooth settings... fingers crossed it works for you!