Some of the buttons in this forum (Create new topic, Post a Reply) are somehow broken: On top of the actual image, the textual description of the button is rendered as white text. When the button is hovered, it is clearly visible as the colour changes to red.
Comparing the CSS of the buttons in this forum with those using a "standard" phpBB theme showed that the markup is something like that
<a href="link to do the action><span></span>alt text</a>
Where usually, the span has the size of the link and a background image applied to it that is rendered on top of the text, so it is invisible for browser, but "displayed" by screen readers or other alternative viewers (or if the button image is unavailable). However, here at the GoW, someone changed the span to be completely hidden and moved the background image to the link, so the text will naturally be shown on top of it, resulting in the described effect.