Error: Winword.exe application error ... (due to editing annotation).

Error:

Winword.exe application error. The instruction at <addr> referenced memory at 0x00.

Cause:

This error occurs when spell checking a Word document containing annotations when embedded in an Excel workbook. In-Place editing is not capable of editing annotations in a document. The speller will still open the annotation window. Microsoft Corporation has confirmed this to be a problem in Word for Windows version 7.0.

Solution:

As a workaround, do not exit the speller when in the annotations pane.