Arduino Cable Problems?

Hi Everyone,
Just last night I was trying to get my lcd to work. It didn't so I'm posting somewhere else for that. I was seeing strangely that the arduino would reset every couple of seconds. I was playing around to see if I could work it, and then I found out there was something to do with the cable. It was a standard cable that fit all of my arduinos but this one. The only way I could upload code or give the Arduino enough power was to shove in the jack into the arduino (fairly hard). Now I am thinking that It might be the jack on the arduino. Any help?

Thanks,
Qtechknow

Check the solder joints with a magnifying class - maybe there is a poor joint one on of the pins.