"POST error-1804:Unauthorized network card is plugged in..." appears on screen even if correct card or no card is installed- ThinkPad Edge
"Post error,1804:Unauthorized network card is plugged in...." appears on the screen at the end of POST and you may not be able to enter BIOS setup. This occurs when your system is below BIOS level 80ET26WW.
ThinkPad Edge 14 and Edge 15
ThinkPad Edge E40 and Edge E50
The CMOS data may become corrupted under certain circumstances, such as RTC (CMOS) battery has no power or using some tool to write CMOS data, etc.
Following these steps to clear and prevent this post error.
Step A). To clear this 1804 POST error:
Remove AC adapter, main battery, and RTC (CMOS) battery.
Reconnect AC adapter and RTC battery,and Power on your system.
Enter Setup by pressing F1 during POST, then pressing F9 key to load default settings.
Select F10 Key to Save settings and exit BIOS, then restart;