Hmm, if you right-click on "C:\Users\Administrator\AppData\Roaming\Opera Software\Opera Stable" and goto "properties", what does it say for permissions on the security tab. Maybe explicitly add the Administrator account to have full control instead of just the Administrators group. Might have to do something similar with "C:\Users\Administrator\AppData\Local\Opera Software\Opera Stable".
Also, if you can find this issue for Chrome when searching Google, the fix might work for Opera too.