Error  generally occurs when an owner of a folder shares a folder, and then clicks on the invitation while signed into the owner's YouSendIt account. I know that's confusing, so here's an example:
email@example.com creates a YouSendIt folder named Music, making firstname.lastname@example.org the owner of Music.
email@example.com decides to share the Music folder with firstname.lastname@example.org.
John and Terry often use the same computer at work.
While email@example.com is logged into his YouSendIt account, firstname.lastname@example.org logs into her email account on the same computer, and accepts the invitation to share the Music folder.
Due to a glitch, this will remove email@example.com's status as owner of Music, and may also cause problems modifying the folder in any way.
We're currently working to fix this glitch, and apologize for the inconvenience. For now, please try to remember not to click an invitation to share a folder if you're logged into your YouSendIt account as the folder owner.