Could just be a mistake, or somebody's interpretation of something you posted. A friend of mine once got a warning like that from Myspace for a pic where she was bending over in a bathing suit. All the while there are probably millions of pics in other profiles that display actual nudity. It must just come down to whatever they happen to stumble across, or whatever somebody submits a complaint about. Did your account get deleted? Just make a new one lol.
few days ago, I got image comments like this http://img68.imageshack.us/img68/4135/copyofcmz1.jpg with the link to http://securedhi5.com/hi5/hi5.htm (I think it's account hack site) don't know if these kinda images cause me account suspended
Things are not good or bad. People are. I don't use hi5 etc. but I got suspend or banned I don't know once, when I tried to login to my tinder account after a year or so. May be I wasn't active so they suspend my account or someone msg me and didn't get a reply so report. the reasons could be many. But mostly, its someone reporting about your pic, or profile.. signup again. no big deal. i don't think hi5 has a problem with that.