Welcome to CD Freaks Tom.
Slow burning is usually down to 2 things.
Firstly DMA not being enabled properly, which I suspect is not the case as the CPU load is very low. Running in PIO mode tends to push the CPU load right up.
Secondly , and probably the cause here, that the burner's firmware doesn't recognise the media & so burns at a slow default setting - typically 4x.
I'd guess that you're using different media than last year so what media have you got this time? Nero's CD/DVD Speed using the disk info tab will give the Media ID & the burn speeds available.