How did you change it?
If you pressed delete at the end then everything following it would be shifted forward by one and in all likelihood break the game.
Most would instead try with a space at the end, or maybe some punctuation (be careful with this though as not all games will have everything here and you don't want to cause encoding issues on top of this, or perhaps instead of this).
Also that does not rule out encoding issues.
Worked example I see a lot in newer systems but could apply here as well
Japanese has many ways of encoding language in hex but a popular one, one seen in several games as well, is shiftJIShttp://www.rikai.com/library/kanjitables/kanji_codes.sjis.shtml
See all those nice Roman characters in that? They are not the same as the ASCII standard most people in English or European language countries are familiar with ( http://www.asciitable.com/
) and likely what your hex editor stuffs in there when you type with it.
While many games nominally use ShiftJIS they don't all support ASCII text (or unicode which is sort of an expansion on the concept) despite shiftJIS on PCs doing as such. You type in ASCII and it will have no clue what to do half the time (and thus crashes and so forth).
This is why the use of hex editors for anything like this are discouraged unless you know all this, and in that case you probably still don't want to do more than a typo where tow chaaracters gto enterde in teh wrogn ordre.
This is also why all those "learn to hack" documents spent an inordinate amount of time going over what a table is and a pointer is.
Oh and yeah there probably should have been a fourth one there. Psyklax covered the start of it -- it might well have been that a string of text could be a file name or something and thus you broke it that way. Most people learn whether this is the case when doing the swap a couple of characters around trick though.