As I note, I was using WoWAceUpdater to keep my addons updated lately. I downloaded the latest ItemBonusLib and put it in the ItemBonusesFu and it solved the problem. I guess ItemBonusesFu hasn't been updated with the latest lib on the SVN yet or something.
I'm having the same error in ClockFu right now, and I've redownloaded all my addons again without fixing this problem. I know it's not ClockFu itself that is causing the error (I've logged in with only Fubar and Fubar_ClockFu running and it worked perfect), but rather some other addon that is tainting it. Has anyone else seen this problem in the past few days and figured out the conflict? Even though it's pretty much identical as above, I'll repost the error:
Error occured in: Global
Message: ..\AddOns\FuBar_ClockFu\ClockFu.lua line 204:
AceConsole-2.0: args.color: "name" must be a string
FuBar_ClockFu\ClockFu.lua:204: in main chunk
Someone in another thread noted that externals will not force a mod to be marked 'updated' by WoWAceUpdater (changes to externals don't bump the revision number for the mod that depends on it). What you might want to do is set your prefs in WAU to skip the version check, and force it to re-download everything, at least once. This corrected a lot of strange inconsistencies for me (including ItemBonusesFu). No need to download additional libs or fix anything by hand after doing this.
My problem in particular, with the error pasted above was definitely ChatMOD using the SVN'd version. I went through and skipped version checking on the updater and updated everything (I do it about once a week anyhow) and consistently get that error upon logging in. But again, my problem is with ChatMOD so I'll wait on that author to fix it though he's not able to reproduce the problem yet.