I'm not a coder by any stretch, but I do occasionally have to do things with very large text files.
Normally when in Windows I'll use Notepad++ since I'm most familiar with it. When I encounter a file it chokes on, I've had very good luck with EmEditor
Since it doesn't keep the entire file in RAM it can handle huge files. It's not free however. A single license will set you back somewhere around $45 USD. Last time I looked they had a full featured trial copy available for download. Wouldn't cost you anything to try it out on your file first.
Might be worth a look if somebody can't point you to a freebie.
If I were working in a NIX environment, I'd just use VIM. Never found anything it couldn't handle.