This is not an problem but the way Microsoft User Interface presents interlaced video modes. The graphics driver interface returns 60Hz/interlaced to the User Interface but it presents such mode info by halfing the refresh rate if it's an interlaced video mode. So 30Hz is indeed 60Hz/interlaced and 29Hz is 59.94Hz/interlaced.
Only 29hz and 30hz can be selected on a TV at Change resolution attribute in Windows Vista
Updated 12/14/2007 01:41 PM
Why can I only set 29hz and 30hz on my TV at the Change Resolution attribute in Windows Vista?