how to replace the uninstallation part of an MSI - uninstallation

Question

I've build a msi installer using a VS2010 setup project.
Now the project does not deinstall because of a "1001 Exception: Invalid format for argument machineName" (see below) inside a custom action.
I am unsucessful at uninstalling the application using the remove from the system control or msiexec /uninstall.
Is there a way to force uninstallation?
Details:
As part of a custom action I register a custom event source which my app uses for event loging into the windows log:
public override void Install(IDictionary stateSaver) {
base.Install(stateSaver);
EventLog.CreateEventSource("VeodinRecorder","Application");
}
inside of the "Uninstall" I try to remove this Eventsource with
if (!EventLog.SourceExists("VeodinRecorder"))
EventLog.Delete("VeodinRecorder"); `
The EventLog.Delete also takes machinename as second argument
So I tried to overwrite the msi used for uninstallation with msiexec /fv and changed the uninstall action:
EventLog.Delete("VeodinRecorder",".");
EventLog.Delete("VeodinRecorder","Application");
I even left the whole "uninstall action" blank.
But nothing seemed to work.
Any Hints?
The full log:
Error 1001. Error 1001. An exception occurred while uninstalling. This exception will be ignored and the uninstall will continue. However, the application might not be fully uninstalled after the uninstall is complete. --> Invalid format for argument machineName.
MSI (s) (60!68) [22:49:00:101]:
DEBUG: Error 2769: Custom Action _3C1D0358_8969_4B01_B8FA_B6B43F4E9E4C.uninstall did not close 1 MSIHANDLEs.
The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 2769. The arguments are: _3C1D0358_8969_4B01_B8FA_B6B43F4E9E4C.uninstall, 1,
CustomAction _3C1D0358_8969_4B01_B8FA_B6B43F4E9E4C.uninstall returned actual error code 1603 (note this may not be 100% accurate if translation happened inside sandbox)
Action ended 22:49:00: InstallExecute. Return value 3.
Action ended 22:49:00: INSTALL. Return value 3.

Answer 1

It seems that the CustomAction.dll was not updated when I update the installation with msiexec /fv.
I now manually placed the newly build CustomAction.dll (with an empty uninstall override) into the installation folder and was able to uninstall.
Update: (Credits to #pcans) use ORCA to edit the currently installed msi and manually disable the uninstall custom action.

Answer 2

Just for reference I want to add that you can also patch the installed product with a minor upgrade to remove any faulty actions in the uninstall sequence before it gets called. This works because a minor upgrade is a reinstall of the same product, and not an uninstall and a reinstall of a new version (which is a major upgrade). You hence replace the uninstall sequence with a correct one before the erronous one gets run.
Creating the patch is quite complicated though, even with professional tools such as Wise or Installshield, but in certain cases this is the only fix that works to get the package properly uninstalled. A package "in the wild" in a company should be fixed this way.
Finally you can use msizap.exe from Microsoft to unregister a whole faulty package from the Windows Installer database, but this is not good since changes to the system are not rolled back at all and lots of junk is left everywhere. The tool itself also seems a bit shaky at times, sometimes creating new errors that are really difficult to fix. Preferably use it for debugging only.
One further note in this already long reply: a special case is when you run a custom action only during the uninstall sequence, and it then returns a faulty return code - sometimes even if it performed its operations ok. These actions can trigger a very annonying "uninstall only rollback situation". Effectively your uninstall is rolled back when it hits the custom action that was never run during install. This will rollback the uninstall and hence work as an installation - your product is left on the machine. Quite strange.
The bottom line: skip return codes for custom actions that are run during uninstall, use other verification mechanisms to ensure the action succeeded.