I have seen a few of these, dont know the solution works 100% of the time, but if you are willing, lets try two things.
1. upon bootup, press F10 to go into the System Services screen. Once you are in there, scroll down to Hardware Configuration, hit enter on that. on the right side of the screen, one of your choices should be Delete configuration and reset defaults. READ the warning, if you are OK with it, check the box and then click Finish. Then try your update again. If it fails, try step 2.
2. download the USC repair file at www.dell.com/.../poweredge-r710
login to your idrac's web page, then in the left tree, select Idrac settings, then in the right side, select the Update tab (in black). browse to where the file is that you downloaded, then click the upload button. Assuming it uploads, then click the next button. it will start the repair process. If this fails, repeat a couple of times. Please let me know which process resolved the issue for you (if it does).
3. please try shutting down system gracefully, then remove power for 1 minute, reconnect power (the system should not auto power on at this point), wait until the LCD on the system responds to button press, THEN power on the system and reflash the bios.