if the bios update didnt contain any groundbreaking advances that you need (or fix any bugs that you have) why not just grab a copy of your old bios and flash back to original.
am still running original bios here as later versions only add support for cpu's faster than I have (or intend fitting) and fix bugs that dont affect me
should say that I am a great believer in "if its working ok dont change anything" to the point that I still have 4 web servers in operation with the following spec.... AMD K6 500 cpu, 256Mb ram, 6.4Gb Hdd, (these days thats laughable, until you think that these machines are still taking the full load of 400 websites each (averaging 15 million hits per day per server), and they only need rebooting about once every 6 months and I have never had to replace anything on them in 8 years. (then compare my other servers for streaming media, quad xeons 2gb ram, 160Gb hdds, these seem to fail every couple of weeks)