iTunes 7.1 breaks helper apps!
Just updated to iTunes 7.1 and ouch... have realized very quickly that Apple snuck in some significant change(s) to its backend/scripting interface, which negatively affect or outright break many (all?) of the iTunes helper apps we've grown to love!
My personal (short) list of broken/impacted apps:
1. iSproggler [sic] - an Audioscrobbler (http://last.fm) client. iPod support appears to still work, iTunes support seems to be suffering from some major hiccups. Basically, it seems iTunes plays are now only reported to last.fm after you connect your iPod, then eject it.
2. gdTunes - a Google Desktop gadget for iTunes. Is no longer able to connect to iTunes, and therefore unable to display what you're playing in your Google sidebar.
3. iArt - a handy-dandy utility I use to auto-add lyrics to my iTunes tracks. It now crashes at startup with a COM exception.
4. Any iTunes automation Javascripts I've tried (like the ones at http://ottodestruct.com/blog/2005/10/20/itunes-javascripts/) crash the Windows Script Host immediately. The error states that WScript "Could not locate automation class named "iTunes.Application".
5. iTunes Art Importer, which is a... um... iTunes art importer. Crashes at startup with an unhandled exception: "QueryInterface for interface iTunesLib.liTunes failed."
Check your favorite helper apps & plug-ins... are they working?

