Correction: the problem first appears in Opera 26, Opera 25 installs and uninstalls correctly.

OS: Windows XP Professional x64 edition

I install Opera along with a lot of other applications via batch file using the command:
Opera_27.0.1689.54_Setup.exe /Silent /NoRestart

However with Opera 27 the installer never terminates and hence the batch file becomes stuck, I had to kill the process using Windows task manager.

Similarly if I try to uninstall Opera 27 the uninstaller does not terminate either and hence add/remove programs is frozen, once again I had to kill the process in Windows task manager.

This problem did not exist in Opera_26.0.1656.60_Setup.exe