Fetching Preview error with some messages

[oSa]

Hi, I'm using SMF 1.1RC2. I've this "fetching preview" problem since I installed this version. At first i thought the problem was a general one but now i found that this problem occurs when the previewed message includes some specific characters like "ğ", "ı" and "ş". If "ğ" is used in the message, preview function doesn't work at all, if there is no "ğ" but "ı" and "ş" then preview works but "1" and "_" characters are displayed instead of "ı" and "ş". All other characters are ok. I'd appreciate if someone could help.