My iPhone will charge on a dock but not with a cable

Hiya,

A few weeks ago my iPhone charger stopped working, so I went into town and bought myself a new one. It stopped working 2 days ago, so in the meantime I decided to charge it with my dock (It's like a radio with a charger on the top), and it worked fine. I went into town and bought a new cable today, and the cable did not charge the phone, it vibrates, shows the charging icon at the top and then the message "This accessory may not be supported" comes up.

If anyone has any solutions, they would be greatly appreciated!