When the "button_text" property is set in a element, the button text is the text given for the input field - e.g. "C:\Program Files".
I reproduced this problem in 2.3, using the sample file Samples\ExeSetup\Configuration.xml:
<control type="browse" button_text="Browse" >
Although this looks like an easy problem to catch, I tried to track down the problem in the code but I couldn't figure it out. This time I won't be able to submit the fix - sorry.