One or more folders in your mailbox have name conflicts with others or system reserved names.
Folders with these names can't be downloaded by your IMAP e-mail program.
Junk
Please connect to your mailbox using your Web browser and rename those folders. Once renamed, those folders will be displayed in your IMAP e-mail application correctly.
My toddler deleted my email app this morning and I reloaded but but tried a few different apps before I realised how to restore the Apple one - have I screwed something up?