Could you please send the number of the Windows update installed on 18th of August?
Could you please check if there is any other installed chemistry addin (e.g. ChemDraw for Excel, ISIS for Excel, Isentris for Excel, Accord for Excel etc.)? Sometiems other chemistry addins can cause problems at loading JChem for Excel addin. The problem usually can be solved by disabling/removing other chemistry addins.
If there is no other chemistry addin, then please try to uninstall and re-install the JChem for Office.