Tribute starting problems

Hi, after sitting idle for several weeks, my 2001 Tribute wouldn't start. All I got was clicking when the igntion key turned. The following day, I got nothing at all. A boost got the car going but after several hours, I was back to square one. I replaced the battery three days ago and the problem appeared to be sorted, and as late as last night, the car was running fine. This morning, however, I've returned to a single click when I try to start, although all dash lights, etc appear bright. I'm now thinking there must be a problem with the starter motor - any thoughts, anyone?

Better check the cables and grounds with a volt meter, before you start going in the wrong direction. Best to test and not guess.