have had this problem. Thought I need to reinstall and then took off previous versions. Finally, when I selected task by Row Number the inactivate button became active.
Do you still have the Backward Compatibility mode enabled on your project Server 2010.
Check under Server Settings >> Additional Server Settings
Inactivate feature is disabled when the BCM is enabled.
Be careful about disabling the BCM, though. You CANNOT re-enable it once you disable it.
Did you ever solve the Inactivate Task Problem? I recently migrated a large (3500 tasks) project from 2007 to 2010 Professional (2010 basic doesn’t have the “Inactivate” button or feature) and have had problems since. Now that I’ve migrated, I can’t get Task Activate / Deactivate to work. I followed the thread of your experience, but no one ever solved your fundamental problem. The inactivate task button always grayed out. 2010 is a buggy beast.
I created a dummy project and the function works fine – I can activate or deactivate tasks at will. But, my Project files that were created in 2007 do not respond. I find it frustrating that migrating a project over adversely affects the features.
Can anyone enlighten me? Thanks! Todd