Recently some of our users in were getting below issue while opening the office file.
Issue: When opening an Office 2010 file from a SharePoint 2010 document library a client side certificate can prompt asking to choose a certificate. Hitting cancel on the prompt produces a read only document.
The PSS engineer carried out below action on the WFEs server
1. On the WFEs server launch IIS Manager
2. Expand down to sites and click on the problem site
3. On right side under IIS choose SSL settings
4. Change Client certificates setting to Ignore