Microsoft SQL Server says my login is disabled, even in single user/DAC mode
I have had the exact same problem and tried this solution and it works: Using PSExec (a free download from Microsoft) to connect to an instance using the NT AUTHORITY\SYSTEM account. Sample syntax:

PsExec -s -i "C:\...\Tools\Binn\ManagementStudio\Ssms.exe"


This will launch Management Studio as a Windows account that has native sysadmin permissions, and this will allow you to switch to mixed mode, enable the sa account, reset the sa account, add your own Windows account as an administrator, etc.

A lot more information can be found in the following article:

http://www.mssqltips.com/sqlservertip/2682/recover-access-to-a-sql-server-instance/

However bear in mind that you may be breaking some contract, just wanted to note it. :)