Let me explain further. Bitcoin is not
a virus. What you have experienced is know as an anti-virus 'false positive' identification.
"A false positive is identifying a file as a virus when it is not a virus."
This often happens with 'new' software because anti-virus programs have never seen the program before. Anti-virus programs use Heuristic-based detection to try and identify unknown viruses, they basically guess if a program is malicious or not to try and 'protect' your PC.
Anti-virus programs are somewhat simple in this respect, however they must enforce an "It's better to be safe than sorry" policy to secure their customer base.
Maybe one day they will accept Bitcoins as payment for their products.
You received the NCIS Error because NOD32 incorrectly thought Bitcoin was malicious, when it is not and interrupted the installer .exe.
NCIS stands for Nullsoft Scriptable Install System. This is what is used to 'build' the .exe from the Bitcoin 'code'. Basically NOD32 stopped it from being 'complete' and functioning correctly, by mistake. See: http://nsis.sourceforge.net/Why_do_I_get_NSIS_Error
You may also need to add the bitcoin.exe process to your 'allowed' / 'ignore' list in NOD32 for it to function correctly.
Hope this helps. Bitcoin is certainly not a virus. It just uses a lot of CPU power when running atm.
Welcome to the world of software development.