Unfortunately I was prevented from using my licence key for the 1.61 buggy version to register the working version 1.64, so I uninstalled the (also buggy) 1.62 licensed version from my other laptop, installed 1.64 on this one and entered my 1.62 licence key - whereupon I was told that I'd used up all my reinstall permissions and they'd reset it this time but "we will not do it again for 12 months" 
Lord knows if I'll be allowed to install 1.61 on the laptop I took 1.62 from (are you following?
)...
I've never come across this before, where a software company deliberately releases faulty software, takes money for it, and disclaims any responsibility if you didn't check every claimed function of the program for bugs before you paid.
It's not as if just one version was faulty - 1.61, 1.62 and 1.63 all are. So anyone who bought 1.61 is totally stymied because 1.64 is too many versions ahead to be licensed.
Kirill, I appreciate you trying to guide, but the link you provided doesn't give access to beta versions.
As Debut do not support this forum I shall have to seek advice on other video help forums and Facebook. I realise that NCH claim that paid-for support is available, but I no longer trust them.