Do the following then try again

Scan with HijackThis and then place a check next to all the following, if present:


O7 - HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System, DisableRegedit=1
...(Unless you've restricted the use of registry editing, have HiJackThis fix this.)


Now, close all instances of Internet Explorer and any other windows you have open except HiJackThis, click "Fix checked".