Pretty much anything besides the vfire.
Windows wasn't the culprit.
Unfortunately you bought a product that is notoriously (and well documented) as being a lemon.
Presonus continues to deny anything is wrong with these I/O devices even though there has been plenty of public outrage over this product not working properly.
The denial is to be expected though because what are they going to do? Recall the product? No. Refund everyone's money? No. It became apparent early on that this was more than just a simple bug fix....then it became apparent that Presonus couldn't fix it.
Ditch the vfire and go with pretty much anything else otherwise your going to spend most of your time trying to figure out one vfire bug after another.