Thanks for the tip but unfortunately it still doesn't work. It seems to be more fundamental to the way the VBA is running. If I put a break point after the AutoText insertion line and just resume the macro after it stops, the table inserts with the correct preferred width settings. Similarly if I put some code that intentionally errors, e.g.
For lngCtr = 1 To 10000000000#
Next
(this causes an overflow error)
if I then click out of the error message, all is well. Very strange