Help: "iPhone cannot be synced, disk cant be read from or written to"

[yogamonkey]

So all was going well, had new iPhone for 4 hours. Put loads of apps, music, films etc on. Synced with Mail, iCal no problem.

Found another App to download from iTunes and now when I plug in the phone it says "iPhone Cannot be synced, Disk cant be read from or written to"

Is this just an 'iTunes overwhelmed it will pass' thing, or should I be more worried? iPhone still working fine apart from that.

Don't want to restore in case I then get stuck in Activation Limbo, but wondered if anyone had come across this.