While removing Symantec Mail Security for Microsoft Exchange (SMSMSE) 6.5.x on Windows the following error message is displayed:

Error 1722. There is a problem with this Windows Installer package. A program run as part of the setup did not finish as expected. Contact your support personnel or package vendor.
 

MSI (s) (94:00) [14:56:43:300]: Note: 1: 1722 2: Unregister_UIObj 3: C:\Windows\SysWOW64\ 4: C:\Windows\SysWOW64\regsvr32.exe /u /s "C:\Program Files (x86)\Symantec\SMSMSE\6.5\Server\SAVFMSEUIObj.dll"
CustomAction Unregister_UIObj returned actual error code 5 (note this may not be 100% accurate if translation happened inside sandbox)
MSI (s) (94:00) [14:56:47:824]: Product: Symantec Mail Security for Microsoft Exchange -- Error 1722.There is a problem with this Windows Installer package. A program run as part of the setup did not finish as expected. Contact your support personnel or package vendor.  Action Unregister_UIObj, location: C:\Windows\SysWOW64\, command: C:\Windows\SysWOW64\regsvr32.exe /u /s "C:\Program Files (x86)\Symantec\SMSMSE\6.5\Server\SAVFMSEUIObj.dll"
 

During the installation of Symantec Mail Security for Microsoft Exchange (SMSMSE) 6.5.x the parts of product were not registered correctly. Now the uninstaller fails because it cannot unregister this part.
 

Register the part of the product that wasn't registered during the installation.
You will find it in the MSI logs.

e.g.
C:\Windows\SysWOW64\regsvr32.exe  "C:\Program Files (x86)\Symantec\SMSMSE\6.5\Server\SAVFMSEUIObj.dll"