I'm trying to get PrinceXML working on our linux server. However the log file says

debug: font request: Arial
/usr/share/fonts/msttcore/arial.ttf: warning: unknown file format
/usr/share/fonts/msttcore/trebuc.ttf: warning: unknown file format
internal error: no available fonts

Similar to this problem: http://www.princexml.com/forum/topic/2486/unknown-ttf-file-format

file /usr/share/fonts/msttcore/trebucbd.ttf command says: /usr/share/fonts/msttcore/trebuc.ttf: ASCII text

Also I modifed the fonts.css to this just to test with several fonts:

@font-face {
    font-family: serif;
    font-style: normal;
    font-weight: normal;
    src: url("/usr/share/fonts/msttcore/trebuc.ttf")
}

@font-face {
    font-family: serif;
    font-style: normal;
    font-weight: bold;
    src: url("/usr/share/fonts/msttcore/trebucbd.ttf")
}

@font-face {
    font-family: serif;
    font-style: italic;
    font-weight: normal;
    src: url("/usr/share/fonts/msttcore/trebucit.ttf")
}

@font-face {
    font-family: serif;
    font-style: italic;
    font-weight: bold;
    src: url("/usr/share/fonts/msttcore/trebucbi.ttf")
}

@font-face {
    font-family: sans-serif;
    font-style: normal;
    font-weight: normal;
    src: url("/usr/share/fonts/msttcore/arial.ttf")
}

@font-face {
    font-family: sans-serif;
    font-style: normal;
    font-weight: bold;
    src: url("/usr/share/fonts/msttcore/arialbd.ttf")
}

@font-face {
    font-family: sans-serif;
    font-style: italic;
    font-weight: normal;
    src: url("/usr/share/fonts/msttcore/ariali.ttf")
}

@font-face {
    font-family: sans-serif;
    font-style: italic;
    font-weight: bold;
    src: url("/usr/share/fonts/msttcore/arialbi.ttf")
}

@font-face {
    font-family: Arial;
    font-style: normal;
    font-weight: normal;
    src: url("/usr/share/fonts/msttcore/arial.ttf")
}

@font-face {
    font-family: Arial;
    font-style: normal;
    font-weight: bold;
    src: url("/usr/share/fonts/msttcore/arialbd.ttf")
}

@font-face {
    font-family: Arial;
    font-style: italic;
    font-weight: normal;
    src: url("/usr/share/fonts/msttcore/ariali.ttf")
}

@font-face {
    font-family: Arial;
    font-style: italic;
    font-weight: bold;
    src: url("/usr/share/fonts/msttcore/arialbi.ttf")
}

How is this can be solved? Any pointers?

Can you run "file /usr/share/fonts/msttcore/arial.ttf" (or Arial.ttf, if arial.ttf is just a symbolic link).

It should say:

arial.ttf: TrueType font data

Yeah, It is saying ASCII text. So it might be fonts installation problem?

Yes. You could take a look at in in a text editor and see what's going on.