Street Triple won't start

Hello,

I just installed the battery (which I charged all winter) into my 2008 Street Triple but it won't start:

When I'm turning on the ignition, there's no sound from the fuel pump, and when I push the starter button, nothings happening. The instrument cluster is completely blank as if there wasn't any battery connected at all.
I connected the battery booster, but still nothing.

I checked the fuses: all are okay.
And before you ask: yes, the kill-switch is in the correct position ;-)

Then I tried the indicator&horn: works!

Any idea what's wrong?

Many thanks