Internet valt uit / Lag spikes

Hi,

Pardon my english, but I'm a foreigner.
I'm having real struggles with my internet connection.
I get disconnected constantly, and randomly (From Steam/Skype, but also failure to look up pages). This also causes me lagspikes that make most multiplayer games, well, unplayable.
My local network seems to be fine (I have the Ubee EVW321B btw).
Is there a way to make sure the problem is not in my side before I contact Ziggo?

Thanks in advance ^^

First disable the firewall in the router. Also connect you're modem with a short cable to the data/tv splitter which should be mounted on the AOP (the box where the green cable is coming in).