I don't know the answer but some more diagnostic information which may or may not help:
* The truncation remains even when I resize the window to create scrollbars and scroll to the right
* The issue doesn't depend on the window size, making it bigger doesn't seem to effect the amount of overlap or truncation in any way.
My guess is that the problem is my widescreen but that could effect fonts etc I suppose.
To work out how wide and high some text is wouldn't you be using a Windows (or .net) API, perhaps the bug is in there as you seem to be positioning the "Make a donation" text knowing the window width and text width (one or both or these values must be wrong)..
Anyway, not a big issue for now...