This sounds like a hardware compatibility issue caused by the use of several different adapters HDMI > DVI > VGA. VGA is not natively supported, so it is most likely the problem with the 470. HDMI > DVI should work just fine with the 470 though.
HDMI is a purely digital interface that is compatible with the digital part of DVI. It's doubtful that it is supplied with the "expensive" DAC needed to run VGA. A proper HDMI to DVI adapter would've been impossible to connect to a DVI to VGA adapter without damaging it. The VGA signals are provided by the four pins at the bottom of the adapter, and is usually provided by the card's RAMDAC.
The pins look like this
: | :
The thing at the centre is ground, while the four pins provide analogue RGB and sync.
Your best bet is to get a DP to VGA or HDMI to VGA adapter. Those things come with a DAC. Even if your card has a DVI port, there is no guarantee that a DVI to VGA adapter will work as a lot of the new ones doesn't come with the necessary analogue pins.