I know Nige...real shame since the Ivona voices are some of the more realistic TTS voices on the market.
They do work well with other software that does not use those Haptek avatars but hopefully, Robert and
his "team" will come up with something soon that can use TTS voices from a variety of manufacturers.
You might also check out Cereproc. They also have some very realistic TTS voices for sale.
Off the cuff, My Windows 7 does not play well with Haptek at all. Slow response, jerky / delayed movements.
I basically quit using it altogether! (Haptek...not Win 7...

).