lead import fails with "There is no action by that name"

When we import more than 200 leads from a single spreadsheet the import eventually fails with an odd message "There is no action by that name" in the view itself.

this morning, 278 of 285 imported before this error popped up.

I am not able to find what is causing the error.

The Text is defined in include/language/en_us.lang.php and corresponds to a LBL_NO_ACTION

which in turn is used in 

include/MVC/Controller/SugarController.php

and

include/MVC/View/views/view.list.php

 

Does this message have anything to do with the import process, or is the import timing out somehow and the message appearis because the the list view cannot be loaded because it is trying to refresh a view where the Metadata is no longer available?

FrancescaS