VideoStudio :: CUDA Acceleration Option Greyed Out

I have VideoStudio Pro X5 Ultimate (full paid for version) but I am unable to select the 'Enable Hardware Encoder Acceleration' option under Preferences/Performance as the option is greyed out.

I have an nVidia GTX660 Ti 3GB made by EVGA. This has a CUDA based CPU and according to Corel's advertising, VS Pro X5 is designed for this chipset, and so I cannot understand why the option to enable it is not available.

Some comments from Corel support I found that this option isn't required for CUDA cards as they are enabled and used by default. However, I have just done a test render of a 1920x1080 AVI clip to MP4 using H.264 and monitored both my CPU (dual Xeon E5420) and GPU utilisation. The CPUs hit 90% whilst the GPUs sat there doing nothing at all other than basic screen rendering rather than any encoding. Corel's comments are incorrect.

Also, I have a support case open with Corel but TBH, I don't hold out much hope as their last response was "If the hardware acceleration options are greyed out, then your graphics card software is managing the hardware acceleration. Please check with Nvidia whether there is an option to disable this. If there is, then once it is disabled, the hardware accelerations option will become active again.". Now, I don't pretend to be an expert in these matters, but I was under the impression that the hardware was enabled and managed by the drivers, and those drivers also offered out the functions of the card to other software that required it (API?), such as VS Pro when it needs access to the hardware acceleration to encode video. Graphics rendering on games works fine without me having to disable any graphics card software so why doesn't VS Pro?

For info, my hardware / OS is as follows:

Dual Xeon E5420 CPUs at 2.5Ghz (8 cores in total)
16GB RAM
EVGA nVidia GTX 660 Ti 3GB (with 310.61 beta drivers but still same issue with 306.97 release drivers)
240 GB Kingston SSD
Windows 7 64bit Ultimate with SP1

How to get hardware acceleration enabled using a GTX 600 series card? Or any other card that initially had the option greyed out?

I know that some people say that CPU rendering gives better quality, but I have a few hundred hours of old VHS and Video 8 tapes to transfer to digital and burn to DVD so as the quality isn't great to start with, I'm not too concerned about a few artifacts if I can significantly reduce the rendering time.

If I can't resolve this issue then I am going to claim a refund under Corel's 30 day money back guarantee as the product doesn't perform as advertised. However, I'd prefer to get it working as I quite like it.