Seems to be an issue with vc2008 as earlier versions and other compilers don't produce the same problem. If the executable has a manifest for 'kiddie control styles' then the tooltip works as expected.

If you'd like to add the manifest, add the following, including quotes, to project settings -->linker--> Manifest File-->additional dependencies:
Code:
"type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='x86' publicKeyToken='6595b64144ccf1df' language='*'"