My tier prizes are suddenly saying Illegal module(ship already over maximum) and not giving me any bonuses anymore.
What's wrong?

It sounds as though you have too many modules for the decks your ship has. Did you just change race from Sillixx to something else?

Ah, no. I got a Psionic Amplifer from a mission reward that was automaticly installed.

So the deck capcity is the problem...
I'll work on that with my next rank up.

You SHOULD only need to add 1 deck beyond everything you have that takes deckspace and your problem should go away. If not, I would recommend you contact Dan with the Report/Contact This App link.

the psionic amplifier is one of the weird modules that is 10-space and i think it automatically installs itself..

you'll have to temporarily uninstall something until you get 10 more decks

or you could unequip psionic amplifier which sux...

that would fall under "something"