Welcome, I have not reviewed all the suggestions given in the above post. However, I would suggest the following if the above does not help
Run a full anti virus scan
Download and run a full, updated scan with Malwarebytes.
If that does not help
Try with another browser.
Finally try a clean boot. How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
Actually, now that I think about it try the clean boot after the scans, It may be your antivirus stopping the attachments from opening. Be sure to untick your anti virus, too with the clean boot.