I am experiencing the same symptoms reported as this closed bug, but not using any 'alerts'. What is causing the error for me is just setting my AJAX timeout before the query. Here is my event sheet:
This pulls my highscores just fine in Chrome & Firefox, but IE v11 shows "There Was An Error."
It does not matter what I set to the timeout value, the AJAX On Error hits immediately, but only in IE.
Removing the 'Set Timeout' action eliminates the problem.
Construct 2 Version ID
EDIT: Ungrouping the events makes no difference -- the error still occurs.