Razor - Unhandled expection(Answer fast, please)

[OLStefan]

When I want to play "Ultima Online" with my razor programme, appears this text:
System.ArgumentException: The output char buffer is too small to contain the decoded characters, encoding 'Unicode (UTF-8)' fallback 'System.Text.DecoderReplacementFallback'.
Parameter name: chars
at System.Text.Encoding.ThrowCharsOverflow()
at System.Text.Encoding.ThrowCharsOverflow(DecoderNLS decoder, Boolean nothingDecoded)
at System.Text.UTF8Encoding.GetChars(Byte* bytes, Int32 byteCount, Char* chars, Int32 charCount, DecoderNLS baseDecoder)
at System.Text.DecoderNLS.GetChars(Byte* bytes, Int32 byteCount, Char* chars, Int32 charCount, Boolean flush)
at System.Text.DecoderNLS.GetChars(Byte[] bytes, Int32 byteIndex, Int32 byteCount, Char[] chars, Int32 charIndex, Boolean flush)
at System.Text.DecoderNLS.GetChars(Byte[] bytes, Int32 byteIndex, Int32 byteCount, Char[] chars, Int32 charIndex)
at System.IO.BinaryReader.InternalReadOneChar()
at System.IO.BinaryReader.Read()
at System.IO.BinaryReader.PeekChar()
at Ultima.StringList..ctor(String language)
at Assistant.Language.Load(String lang)
at Assistant.Engine.Main(String[] Args)

Who can say me what to do????