I recently had a 20 megabyte HTML file with very long lines of text. Almost all 20 megabytes was on a single line in the file. My favorite editors Visual Studio 2010 and Notepad++ both were unable to handle it. Visual Studio consumed more and more memory, up to 2 gigabytes before I killed the process. NotePad++ was happy to consume only 200 megabytes, but after 5 minutes of churning away with no sign of progress I gave up on it to.
After some initial googling and swearing I came across EmEditor. It handled loading and searching the awkwardly sized file with no problems. It’s a new tool I will definitely keep in my tool belt for the future!