I had this, among a couple other issues, with a Jag CD I bought. What I ended up doing was opening the Jag CD and cleaning the fingerboard that inserts into the bottom of the Jag CD (inside) and inserts into the cart slot of the Jag. Strangely on the edge connector inside my Jag CD there was a large, dead bug. How it got inside is beyond me, but this should solve your issue, of course assuming something isn't hosed with the power jack itself. The Jag CD gets a bad rap for being unreliable, but generally speaking a good cleaning will fix most issues. Of course the games still stink, but that's another matter