Trademarks are not enforcable across totally different products, at least not that I'm aware of. (Mind you, I'm not a lawyer, so what do I know, anyway?)
Second, trademarks =HAVE= to be enforced to be kept. If Nutella is claiming a trademark violation after several years, then the courts may well end up saying that they've lost the trademark completely. This is brave of Nutella, but very stupid. They'd be much better off saying that Gnutella falls outside the scope of their trademark, to guarantee that their trademark stays intact.
Last, it might well result in a lot of publicity for all the non-family stuff that Nutella wants to distance itself from. Which might encourage journallists, always on the look-out for a sensational new story, to start looking into exactly =why= Nutella is so nervous...
Summary: Nutella's either dead or undead. If the latter, apply holy water.