For the last few months, my layout has been wired, not completly, but enough to run the entire layout. I havent ran trains for a few weeks, and last night, when I wanted to, all of the locos would not perform well, they were all sputtery and at spots, would just stop, if i gave them a small tap, they would sputter down another foot of track, only to stop again, the wheels and track dont look dirty, and like I say, two weeks ago (at most) I was running them flawlessly. What gives? Any ideas of possiblr problems?