There were two problems with the repro case. First, the text contained characters outside the standard printable ASCII range: 65279, for example. This is what broke the word wrapping. Second, the text contained carriage-return breaks (\r) instead of line end (\n). NGUI works with \n, not \r, and if asian characters are encountered (which 65279 cetainly falls under), all word wrapping is turned off.
Sanitize your text after receiving it from your URL and before passing it to NGUI.