I am having a huge problem with my MacBook Pro.

When the login screen appears and i put my password in, it is not accepted.
BUT, this IS (100%) the correct password and user name. the password has not changed, i am the only person that uses the laptop and i had successfully logged on with the same password and user 10min prior. i had to restart after changing some settings in the program Traktor Duo, (i was arranging some midi controllers to be used in the program).

SO, i soon decided just to reset the password on the account with the use of the start up disk. however im stuck again because when i try to select the admin account from the password reset utility, it is not there. there is only this one account on the laptop and it is not showing up.

so it's almost like during the course of a simple reboot (which was conducted correctly), the only existing account on the laptop has been deleted.

Other details:

1. Reading other forums, i found many people had problems similar to this after a software update. i have not recently had an update.

2. Im not sure if this had any baring on the situation but about a week ago i was playing with the bluetooth settings to connect with my phone and i changed the name of the computer. however this was only the name of the device that would show up once it had been found. AND, i had logged in and out with these settings in place successfully many times.

3. Before you ask i am definite that caps lock is off and i am typing correctly.

4. in 48 hours of searching, i have not found a single thread on any mac discussion forum that talks about this. i have been to both the Apple store in sydney and an authorized reseller and the staff there where dumbfounded (i have the next available appointment at the genius bar but that is 5 days away and really need my laptop for work in the next 2 days at least.)

Reformatting the computer is really not something i want to do, i have so many things on there that i require of work, some are backed up on external HDD's, some are not.

Thank you very much in advance for reading this and for any light you can shed on the issue.