I'm not sure if this will help, but from what I've read, the Fusion Forty may have some compatibility problems with the Gary chip on older revision Amiga 2000 motherboards.
Quoted from a review of the Fusion Forty:
"I had to do the following before I could get the
Fusion Forty to work correctly.
1. Replace the CMOS Gary chip with a new Commodore-manufactured one."
In addition, the Ram does not autoconfigure.
Quote:
"Note that this RAM does not autoconfigure. According to RCS, they don't autoconfigure the RAM for two reasons: so that they can overcome the Amiga 2000's 8 meg
limit, and (they claim) autoconfiguring the RAM would make it slower."
I hope some of this is helpful.