Can't boot with Time Machine disk plugged in

[I_Need_A_Better_Name]

The spinning / at the very start just stops (even before chameleon/chimaera) and the machine hangs. I already ensured the external hdd is not in my boot priorities.
Any ideas?

 

[dddirtman]

i have to ask but is your primary drive in sata0

 

[I_Need_A_Better_Name]

Yes. My motherboard got 4x SATA2 (labeled with 5 to 2) and 2x SATA3 (labeled with 1 to 0) and I used the one SATA3 port with a '0'. :/