I also get a blank Error 500 page (adm gets an Error 401) when upldating from 3.2.10 to 3.3.1 (automatic update package).
Update went through without problem but returing to the index or admin index gives me blank pages. I also tried to upload a vanilla 3.3.1, but it does not help.
When uploading a backup of the 3.2.10-files (but using the 3.3.1-DB) everything works again, but when I try to disable an Ext I get 500/401 again.
Right now I am restoring the 3.2.10-DB.