When it comes to BIOS issues, there are two recommendations I can make. The simpler one is a power drain, unplugging the server and holding the power button down for 30 seconds. The other thing would be an NVRAM clear, which would involve moving a jumper on the motherboard.
Above is the manual for the system. Page 116 has a motherboard diagram. The jumper I'm referencing is in the bottom right corner. You would want to move the jumper to the common pin and the uncovered pin (1 & 3). You would then power cycle the server and that should clear the NVRAM, but this would also reset the BIOS to factory defaults. If this does work, you'll need to set the BIOS back up the way you had it before.