Do you update TL regularly? If not then a change of category, sub category or item specific can prevent an upload, if that is the case do a full version update and then try again.

If your TL is up to date then I can only sugest using the ebay sell your item form, you can copy over the html for the description, and see if that works.

If it is happening with more than one castegory/listing then your TL may have become corrupted. If that is the casee then you will probably have to back up your data base and uninstal TL then redownload it and do a full verion update.