Well I've the same problem with my SAAB and I'm really frustated. I add the link in my Firewall, but still can't install the plane. I've installed the MU-2 and the Jetsream without any problem.
It's an intensive reverse plane on the ground and you can taxi very well with that. Just try to assign an axe of you hardware to control REV and you'll be happy. The MU-2 is by far my favourite aircraft, a lot of pain to master but when you handle it well, it's dream. It's smooth, nimble and very fast, climbs like a rocket and descends are very smooth. She's not a Marquise, she is a Princess but Trim it again and again each time you change power ou CL settings. Sorry for my poor english.