YOu didn't mention how much video ram your machine has, and is it a netbook, notebook/laptop, tablet or desktop?
Some users have reported some goofiness using some netbooks, as well as tablets.
Also, are you using anti-virus software and anti-spyware(Use Spybot Search & Destroy for anti-spyware, nothing else works, honestly, because the rest let their buddies in via backdoors, and it's free!)
I really can't see much wrong with the specs. The CPU and RAM exceed the minimums, which leaves the video card, which I'm suspect is well above specs anyways. Other possible issues might be the hard drive, mainly in regards to health of it as well as possible space issues.
Are you using the December Beta or the September 2010 release? Or something earlier? I think before September 2010(maybe April 2010), there were issues with 64-bit installs. There may be issues with Win7 on those releases as well.
Not to hedge help, but have you purchased the package yet or are you still in test/eval mode? It won't make a difference because the hardware only lets you SEND the data to run your lights. If your software or system is already unstable, adding the MyDMX hardware won't resolve things.
Try doing a removal, reboot, re-install, then reboot then launch it. If you have the hardware, don't boot with the hardware connected, it's been well reported to sometimes be wonky when you boot with the hardware connected. I've had it go both ways, so I know when I boot with it unplugged, I have fewer issues.
Also, anything else you do with that computer? Any other apps on there?