I can only find a [http://s3.amazonaws.com/szmanuals/c551b11cce424bc93b38ce7f3290791a|user manual], and this [http://youtu.be/EyeVjiIJt_I|disassembly video used to "unbrick"] a coby tablet. It doesn't look like Coby has any useful troubleshooting or support pages themselves. [http://www.ifixit.com/Answers/View/124392/Frozen+bricked%2Cwill+not+reset|This post] suggests a longpress to reboot it.
Is there anything else you can tell us about your tablet? Model number, any other symptoms, etc.