Is there a way to change the font used in the game?

I have a problem with the font used in some of the tool-tip windows.

The font changes after a short time, such as after a battle, and becomes almost unreadable.

For example:

The font before

The font after

I have a 27" monitor running at 1920x1080 with an ATI HD6870 on windows7 64bit. I have the Steam version of the game.

I have tried using different AA settings and running in both window mode and fullscreen with no change.

This problem is ruining my enjoyment of the game.

Any help would be most appreciated.