Hey Paulo. You didn't say much about your computer system or software details, but here are a few ideas. Code 43 usually means either there is a driver problem (computer issue) or a device problem (whatever it is you might be plugging into USB). Try doing a complete reinstall of the MyDMX software & drivers. Keep the MyDMX box unplugged from the computer for now. Completely uninstall the MyDMX software installation you currently have. Afterwards, double-check in Device Manager to see that the driver is gone. Now, make sure you have the latest MyDMX version from 14 FEB 2013 -- here is a link:
https://www.dropbox.com/sh/lm3...1h4G/2013%20Feb%2014Download to your computer and do the install and let the install program put in the drivers (and fixture library). Let it finish the install completely. I would suggest then restarting your computer (usually not needed, but just an extra step to ensure all is well). After restart is completed, now plug in the MyDMX adapter box to your USB. You should see a message pop up above the task bar informing you that drivers are installing. When that is done, you can open up the MyDMX program. It should work.
If not, you have other issues that require someone local to you with computer tech support knowledge to troubleshoot deeper into what is going on. Of course it is remotely possible you have a defective MyDMX box....this is where some hands-on diagnostic help is necessary. Best of Luck.