My bet was since wxWidgets 2.8 is quite ancient these functions might cause some problems so you could try to disable them. When you set a custom zoom level in Windows 7 there is the option to do it like Windows XP, thats what i was referring to.
Where have you got this .manifest file from? You need this e.g. for enabling Themed Controls so that your Buttons and Lists dont look like from Windows 95 but usually this file gets embedded into the .exe file, you dont need an extra one. I never used a nightly, i always compile myself, cant remember having seen that file in the output ever, but cant check right now to be sure. What happens when you remove the file?