@AmigoSteve
i wonder if the installer accidently overwrote your radeonHD driver with an older copy. update 4 dates back several months before version 0.53 of hans' radeonHD driver, which i thought was the first to support the 4650, although i could be wrong. or maybe your monitor selection got hosed. either way you could attach a monitor to the onboard graphics or use the early startup menu to be able to access your system and reinstall the most recent version of the driver.
of course i'm just a normal user like yourself, so this is all just guesswork on my part. have you tried asking the developers in the hyperion
support forum? they're usually very good about replying fairly quickly. you can also try asking the guys at
amigans.net, another place where the developers tend to hang out.
-- eliyahu