Quote from mommyof2grlz
My boss is NOT a nurse and doesn't like my verbal style. I'm not a yes man I'm a problem solver a fixer. I try new things. Bending over is not one of them. And especially blindly following I just had a performance evaluation it was great. Don't know what happened!!
Make sure to keep a copy of your eval to offer at job interviews and counter any negative references from where you work now. If you have other references you can just say not to contact your current employer.
To get a final written warning means your manager is doing a paper file to get rid of you and just biding his or her time. Transfer to another dept if you are able, but you may not have that option with disciplinary action in your file. Best bet is to find another job and negotiate a pay raise while you're at it.
As to what happened it sounds like they are tired of your assertiveness and personality style. Management likes yes people not ones that clash or speak up not even for valid reasons!
As to the glowing eval, it is very typical to have that one day and the next to find yourself fired. Unfortunately, it happens all the time. Sadly, not unusual at all!