Been having these same errors on my Dell R510 ever since upgrading to the 6.10 RCs a few weeks ago. I could sometimes get the system to boot and kept hoping that one of the releases would clear the issue up. I ordered a replacement flash drive thinking my drive was starting to go bad as one of the times I performed a chkdsk on the flash drive from my Windows PC and the server booted properly. This trick got the server to boot without any meddling!
My server is a Dell R510 BIOS v1.14.0