Video clips select themselves automatically on the sequence

Hi !

So, here's my problem :

(English isn't my mother tongue, so... I hope my explanation won't be incomprehensible.)

I can't work on a video clip without it being automatically selected ; I don't need to click on it, it just selects itself magically, and I need to unselect it so that I can cut all the tracks at the same time.

Here's what my sequence looks like when I open my project : 

I've just opened it, didn't do anything more, and here's that little clip framed in white. And if I press space, once it moves to the next clip, it will be that next clip's turn. And so on, and so forth. o__o

It's not a HUGE problem, but a) it doesn't make sense, and b) it's still very, very annoying... especially for a beginner, I guess ?

If a nice, chivalrous and enlightened person could help me on this issue, it would reaaally make my day. No, my month !

Alex