When the system keyboard language is set to a non-latin character set (e.g. Greek, Russian, Hebrew) using flash with WMODE set to anything other than window (the default) results in text appearing as-if the keyboard language is US.
Below is a simple text box to try things out for yourself. First a flash object with wmode set to default (which is window), second with wmode set to opaque and finally transparent. Opaque and transparent exhibit the same behaviour.
a Flash textbox will load here with wmode = 'window'.
This piece of flash has the default wmode, you can type using any keyboard setting and see the characters you expect.
a Flash textbox will load here with wmode = 'opaque'.
This piece of flash has wmode set to opaque, if you're keyboard is set to a language like greek you'll find that the characters that appear are those corrisponding with a US keyboard layout.
a Flash textbox will load here with wmode = 'transparent'.
This one has the wmode set to transparent, you should get the same results as the opaque one.
These are links to mov files, i'd suggest downloading them and viewing with VLC or Quicktime.
How to add another language and activate the language selection toolbar (1.1Mb).
Typing with keyboard set as UK then Greek, flash window mode set to window(100Kb).
Typing with keyboard set as UK then Greek, flash window mode set to opaque(84Kb).