Tablet issues, i need advice

I purchased a generic tablet and have had issues from the beginning. Seller has sent me firmware but tablet will not accept it. Im wondering if it might be a hardware issue. Here is what happens after a few minutes of use.
It will either freeze or just shut down. Not sure what to do next. Here are the specs.
Thank you
Model: MID
Adroid: 4.0.4
Baseband: 4.0.14
Kernel version: 3.0.8+
anpei@ubuntu#16
sat jun 16 17:16:38 CST 2012
Build Number: crane_axmid-eng 4.0.4 IMM76D 20120723 test-keys

here is another issue, when I reboot in recovery mode to do a hard reset, the volume buttons will not allow me to navigate thru the menu. It is stuck on reboot so i can not choose to reset.