We are having a fleet of T520's that is completed with the BIOS upgrades and the existing version is 1.26. After upgrade, I found that the functional keys (From F1 to F12) are not working. I tied to press them harder but that was not working. I have tried to press them while boot time but that is not working at that time also. The only technique we have had success getting to the BIOS is through pulling the CMOS battery out and after that flushing power out of system and afterward booting in. We will obtain a BIOS Date/Time error after this and we are provided with the option to bounce through Pressing Enter otherwise pressing F1 to enter into BIOS Setup. This is the only way by which I will be able to get into the BIOS and that is just by pulling the CMOS battery. If you have any solution for this then please let me know that. Thank you so much in advance for reading and replying to this.