What is the cause of the "Internal error to the application" eBay posting error?

eBay responded with the message: Code: 10007 Short Message: Internal error to the application.
Long Message: Internal error to the application.
Whenever eBay has problems processing new posting attempts, this will generally cause the above error. When this error occurs, Selro continues to re-attempt posting of the ebay Item for number times . If you eventually see this posting error in Marketplaces > eBay > Upload Status view, this means that Selro has stopped attempting to post the item. If this happens you have to list the item again using Selro's eBay listing tool. In the end, this posting error can still occur until eBay has resolved the issue.