AFLayoutText causes failure in creating appearance

In Acrobat 11 I'm using AFLayout object to create annotation appearance. I want it to have background and some text on it. Everything seems to run fine but, when I  use also method AFLayoutText as in the sample below it creates null CosObj. Without the text method works fine and the appearance is created correctly. Am I missing something?

Thanks

    ASFixedRect rect;

    PDAnnotGetRect(annot, &rect);

    AFLayout layout = AFLayoutNew(&rect, pdRotate0, cosDoc);

    // border and background

    AFPDWidgetBorderRec border;

    border.nStyle = AFPDWBSolid;

    border.nWidth = 0;

    PDColorValueRec brdrColor = { PDDeviceRGB, { fixedOne, fixedZero, fixedZero, fixedZero } };

    PDColorValueRec bkndColor = { PDDeviceRGB, { fixedOne, fixedZero, fixedZero, fixedZero } };

    AFLayoutBorder(layout, &border, &brdrColor, &bkndColor, false);

    // text

    TextAppearance_t ta;

    SetDefault_TextAppearanceP(&ta);

    AFLayoutText(layout, false, false, &border, &ta, "OK");

    // create stream cosObj

    CosObj cosN = AFLayoutCreateStream(layout);

     AFLayoutDelete(layout);