MS Office security pop-up, calling taskmgr.exe an Excel add-on.
I was editing a very simple Excel spreadsheet and this message popped up. Since when is task manager an Excel Add-on?
I can't say for certain that task manager was running (minimized) at the time, but it's entirely possible. All I know for sure is that after I got the pop-up, task manager was not running.
Check your Add-Ins that are installed. Uncheck all of them and one by one enable them till the time you get an error. Tell us what happens if you do that.
Sid