MonoGame rendering text with black boxes?

I have a UI manager that renders a background image and some images and buttons using BlendState.AlphaBlend. This works as intended. However, when I try and draw some text on top of it with the same BlendState, each character is encased in a black box and it looks awful. I played around a bit and found that BlendState.Additive was the only one that didn't render the black boxes. However, the text is now slightly transparent, which looks weird. I then decided to mess around with custom BlendStates, but after around 10 minutes I found that there could be over 67 million different BlendStates. Hmm. My last thought is that it could be the font that is breaking it, because I tried rendering with the Arial font and AlphaBlend worked fine. Is there a way round this using BlendStates without finding a new font?

tl;dr I can only render text either with black boxes or half transparent.

Text rendering code:

sb.Begin(samplerState: SamplerState.PointClamp, blendState: BlendState.AlphaBlend, transformMatrix: Game.Camera.GetViewMatrix());

sb.DrawString(Game.Font, text, position, color);

sb.End();

SpriteFont File (using the free Minecraftia font):

<?xml version="1.0" encoding="utf-8"?>
<XnaContent xmlns:Graphics="Microsoft.Xna.Framework.Content.Pipeline.Graphics">
  <Asset Type="Graphics:FontDescription">
    <FontName>Minecraftia</FontName>
    <Size>6</Size>
    <Spacing>0</Spacing>
    <UseKerning>true</UseKerning>
    <Style>Regular</Style>
    <DefaultCharacter>?</DefaultCharacter>
    <CharacterRegions>
      <CharacterRegion>
        <Start>&#32;</Start>
        <End>&#126;</End>
      </CharacterRegion>
    </CharacterRegions>
  </Asset>
</XnaContent>

It's a pixelly game (so I need a blocky font to avoid weird antialiasing) and I think the font is a bitmap font. Just in case that makes a difference.

Edit: I found that setting the text size (in the SpriteFont file) to anything other than it's native size fixes the problem (but also renders with antialiasing, which I don't want). Also, this problem seems to happen with other bitmap fonts (tested 'Minecraftia' and '04b03').