Today users started reporting that they could not open Excel files located on our SharePoint site via IE. When a file is clicked, Excel launches and in the bottom a progress bar says "Downloading: filename" but it takes ages, where it would normally take a few seconds.
I found this thread which describes a possible solution, by unchecking a setting in Internet Explorer.
This solution did not work for me.
This issue just started happening today. I checked both client and server for updates/events that happened recently to see what changed to no avail. I've also spent the better part of a day searching for solutions. These include adding the site to our trusted sites list, resetting IE to default, checking for anti-virus programs and many more.
The strange thing is that it appears to be affecting most users but not all. Some can open files just fine while a majority are hindered.
Nothing has helped and I'm out of ideas. Anything helps at this point.
EDIT/SOLUTION: So apparently our antivirus (ESET) updated over the weekend which started blocking downloads from our SharePoint site. You can whitelist IPs in the ESET settings to fix the problem.