Install vm esxi 5.1 problem

Hi, Everyone:

Recently, I attended a VM course and want to make a home lab. I am a fresh user of VM.

1). I install vm esxi 5.1 on the new pc. (montherboard asrock b75 pro 3, i5). The process of the installation is very perfect. No error message. 

2). I install vsphere client on another PC.

3). vsphere client can connect to  esxi server for 1 or 2 minutes. After, It is disconnect.

4). I try to ESXi use DHCP to get IP. I

     I try to ESXi use fix IP.

     I try to seperate. Use standalone switch , connect ESXi and Client.

     I try to reinstall esxi.

     I try to reboot esxi.

     The result is same. "After a while, the client lost the esxi connection. "

5) The screen are post here.

Can anyone help me ? I search for a long time , and can not find the solution.

Thanks !