Norton Insight is not a virus detection but only an assessment or votes by other Norton users about the program (safe or not safe). It's a reputation-based detection only. It is not blocking you to install the program but giving you warning only but you can decide to install, if you believe it is safe program. The antivirus protection by Norton should block only the game installer if it's the antivirus virus detection signature found virus or malware on it. If it's only Norton Insight detecting it, it is only for your information which means, you need to decide yourself.
Please see Suspicious.Insight article in http://www.symantec.com/security_response/writeup.jsp?docid=2010-021223-0550-99
have bought down load for plants vs zombies norton wont let it in said insite network threat, smart screen filter says its ok. bought bejeweled 2 at same time it loaded fine. any ideas?