Hitec astro DC focuser and ascom problem

[red dwalf]

need some help if you can to sort this little problem out, i`ve been using the Hitec astro dc focuser with nebulosity 3 for ages on my windows xp 32 bit desktop, i recently bought a better desktop running windows 7 pro 64 bit and now when i connect it to nebulosity it will work for a couple of steps then stop, works 100 % with the hitec astro software on it`s own so it something to do with ascom, i`ve downloaded the ascom recommended driver from hitec website and they say it is full ok with both 32 and 64 bit machines and i know it worked on my old 32 bit machine, i`ve run it in ascom diagnostics and 32 bit it`s fine and in 64 bit mode it comes up with this message, any help gratefully received.