The only thing I can think about is an issue in your LSL script (please, post the relevant part of your LSL script (the llDialog() call and whatever code initializing the variables used in that llDialog() call), or with your operating system's configured locale; the viewer only knows about English (no UI translators/contributors), and maybe you configured a different (UTF-8 only) locale for scripts (in the "Preferences" floater, "General" tab) ?...
Also, you can use the Lua console ("CTRL ALT L" to pop it up) to test your Lua scripting; in this case, try:
Which should print:
If you get different values, there is a character encoding issue... See
Unicode and Lua.
For any further investigation by me, please also post the viewer log file (with a log obtained running your script with the "Lua" debug tag enabled, via "Advanced" -> "Consoles" -> "Debug tags"); I'm tired to spend time poking in the dark to try and solve your issue...