Don't push to hard in trying to get a system (windows) to bott if it won't as it could cause more problems including on the odd occasion hardware pushed too hard.
The Trojan.gen.2 reminds me of Zeroaccess or Zekos, cidox etc. Where Norton detects part of it, but not all of it due to some malware working deeper in the Boot Sector, partition or other level (like the ROL.)
The intrusion prevention blocking is at times due to the sytem being infected and the infection (or more than 1) is shall we say trying to phone home on the Internet to send data or download more files etc, but Norton is blocking that.
So you could say Norton and whatever it is are at a stand off. Some of the Rootkits and Bootkits do at times cause a non booting Windows or where Windows crashes after a certian amount of time.
Quads