Supported keyboard layouts can be found on page 142 of the Symantec Encryption Desktop Windows User Guide. I have included the list below as well. Unfotunately, Greek is not a supported keyboard layout, so those characters would not be accepted.
.. Belgian (Belgium; Comma)
.. Belgian (Belgium; Period)
.. Bosnian (Bosnia)
.. Bosnian (Bosnia; Cyrillic)
.. Bulgarian (Bulgaria)
.. Bulgarian (Bulgaria; Latin)
.. Bulgarian (Bulgaria; Typewriter)
.. Canadian Multilingual Standard (Canada)
.. Chinese Simplified (China, Singapore)
.. Chinese Traditional (Hong Kong, Taiwan)
.. Croatian (Croatia)
.. Czech (Czech Republic; QWERTY)
.. Danish (Denmark)
.. Dutch (The Netherlands)
.. English (United States)
.. English (United Kingdom)
.. English (US-International)
.. Estonian (Estonia)
.. Finnish (Finland)
.. French (Belgium)
.. French (Canada)
.. French (France)
.. French (Switzerland)
.. German (Germany/Austria)
.. German (IBM)
.. German (Switzerland)
.. Hebrew (Israel)
.. Hungarian (Hungary)
.. Hungarian (Hungary; 101 keys)
.. Icelandic (Iceland)
.. Irish (Ireland)
.. Italian (Italy)
.. Italian (Italy; 142 keys)
.. Japanese (Japan)
.. Korean (Korea)
.. Norwegian (Norway)
.. Polish (Poland; Programmers)
.. Polish (Poland; 214 keyboard)
.. Portuguese (Brazil; ABNT keyboards)
.. Portuguese (Brazil; ABNT2 keyboards)
.. Portuguese (Portugal)
.. Romanian (Romania)
.. Russian (Russia; Cyrillic)
.. Serbian (Serbia and Montenegro; Cyrillic)
.. Serbian (Serbia and Montenegro; Latin)
.. Slovak (Slovakia)
.. Slovenian (Slovenia)
.. Spanish (Spain)
.. Spanish (Latin America)
.. Spanish Variation
.. Swedish (Sweden)
.. Turkish (Turkey; F)
.. Turkish (Turkey; Q)
.. Ukrainian (Ukraine)