I was getting this exception during build while running ant. Googling didn't help much and I was flummoxed because the same code was running fine till now.
My code reads a text file and does some operations on the basis of values read. It was only when I saw the text files I understood the error. I had copied the text in wordpad and saved it as .txt file. Wordpad had put lot of formatting information before and after the content. Also there was "\par" after every line, which was giving this error.
So moral of the story: if you get this exception check your properties file (or any other file that your code might be reading.)