As it turns out, the problem is caused because Automator detects iTunes 10 as being a lower version number than iTunes 9, because Automator apparently sorts version numbers alphabetically instead of numerically.
As it turns out, the fix isn’t entirely onerous: simply open up the info.plist inside the packages of your non-functioning workflows and manually change the version number. If you absolutely can’t live without your iTunes Automator workflows until Apple managed to issue a Software Update, here’s your stop gap solution.
John Brownlee is Cult of Mac's Deputy Editor. He has also written for Wired, Playboy, Boing Boing, Popular Mechanics, VentureBeat, and Gizmodo. He lives in Boston with his girlfriend and two parakeets. You can follow him here on Twitter.