This happened quite suddenly this morning. I noticed that a file was saved without an extension and I went to type it in. I clicked on the file name in a finder window and I typed the extension. Mac came up with the usual "do you really want to add this extension?" and I had second thoughts. I clicked "no" and then I was unable to change the name on any file or folder.
When I click on the file name to change it, the usual blue highlighting appears and my mouse changes to a cursor. I can put the cursor into the file name, but cannot type anything or move the cursor with my arrow/home/end keys.
I am also unable to change the file name in the "get info" panel.
Any help would be greatly appreciated.