I recently ran into this very same problem in which the bcp error message stated:
An error occurred while processing the file “D:\MyBigFeedFile.txt” on data row 123798766555678.
Given that the text file was far in excess of notepad++ limits (or even easy human interaction usability limits), I decided not to waste my time trying to find an editor that could cope and simply looked for a way to pull out a batch of lines from within the file programmatically to compare the good rows with the bad.
Click through for a precise and useful Powershell snippet. The .NET file stream libraries are also good for this kind of thing.