Object creation/selection problems

Working in AutoCAD 2012 student version on XP.
My app took a strange turn. Normally by habit, I select the object I want to modify and then select the action to perform. This eliminates having to select 'enter' after selcting the object you want to modify. This no longer works. Must select the action first. Select an object, hit the delete key, nothing happens. Have used this function since last August when I downloaded the appplication.

I tried reinstalling the app , powering down/up the PC, same thing.

Any ideas? 

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