Same here on my DLO iBoom Travel Portable Speakers. Like String said, it's normal for any accessories which aren't iPhone certified. They work perfectly fine, except the iPhone doesn't recognize it like mentioned in the error message. Will have to bear with it

Regarding your issue where the error comes up without anything connected, may I suggest a firmware restore as an option if things get desperate? Another guy who had the same problem had his unit replaced FOC by his local Apple Store, pity though because we're not in the States.

http://forums.macrumors.com/showthread.php?t=432454

I also read that sometimes it could be due to some crap getting stuck up your iPhone's dock connector. Try lightly sticking a small pin in there and check whether anything's stuck inside, or if you're paranoid, a flush with some compressed air. Good luck, mate!

This post has been edited by Samanoske Akechi: Jul 20 2008, 03:29 PM

Indeed, mate, as grim as it may sound, you're left with 2 options now. The first, and least troublesome, would be a firmware restore. However, this is only a minor possibility as many similar reports of such problems in the Apple Support Discussion section concluded with the owner sending it in for 1-to-1 replacement. You have my blessings, mate. Hit the Restore button and keep your fingers crossed.