Make sure that you define all fonts and are not using symbolic fonts such as "application", etc. If you don't use define fonts, labVIEW will use whatever is specified in your window settings, and will thus depend on the windows theme and OS font sizes.
This has nothing to do with 32 vs 64 bit. As a first step, look at the font size setting of the OS
(Control Panel\Appearance and Personalization\Display)
Make sure it is set to "Smaller-100%" (not 125 or 150%)
As a bandaid solution you could also define the fonts in the ini file of the application.