Hi,
This is a very rare issue and everyone else is having 0 issues dual clienting. I have experienced this myself a while back on as well. Here are the steps I took:
1. Disable UAC settings
2. Right click on "Fkenro.exe" (this is the actual client) and select properties -> Compatibility -> run this program as an administrator
See if that works for you. Otherwise, you could try using mouse freedom (which allows you to exit the RO window without alt tabbing). To do this, just look inside the "Addon" folder in your fRO directory and move dinput.dll outside of this folder, into the root RO directory.
For future reference, the best way to get help is right here through the forums. All Administrators have, in their profiles, their skype contact information. You are free to add any of us for help. Thanks,
Jorge
Note: You can run RO in Windows 8, just Properties -> Compatibility -> Check "Run this program in compatibility mode for:" -> Windows XP