Is Time Machine Acting Strange ? Or ...

Hello,

Every time i plug in my external, and click the time machine icon in the top left bar, it ALWAYS says "Encrypting Back Up Disk" and its always only at 1% .. The thing is that it will give me this message BEFORE it actually starts backing up the data.

What does this mean, and how can i disable it ?

Additionally, i've already put a password lock on the external HD itself, so i don't understand why it needs to "Encrypt" every single time ?