How to I get rid of "Error with menu entry.... " in recent log messages?
Same problem here:

I just created a Vocabulary and set to sync with the Main Menu. When saving the Main menu doesn't show the terms of the vocabulary.

I get this error in the logs: which is fired by the line 1190 of taxonomy_menu.module


  Error with menu entry "" in menu "main-menu"


The vocabulary is set to:


  Translate. Different terms will be allowed for each language and they
  can be translated.