I received some reports that the transparency feature called Aero automatically turned off on some users. This problem maybe due to incompatibility of some softwares that uses their own technology e.g. WinAmp (according to users) and other freewares.
To fix the problem, It is recommended to update your software to the newest version.
Workaround using the newest version of WinBubble
You can reset the Desktop Window Manager using WinBubble to be able to restore the feature. Simply click ON at the Optimize Tab and it will automatically restore the aero functionality.
Tested after a Windows 7 64-bit user asked about the problem and WinBubble easily restores the Aero function in just one click!
Hope this Helps!