On several occasions I've found that mysterious new problems were linked to either browser or Microsoft Windows updates. Check when Windows updates were last applied on the affected workstations. If the timing of the updates corresponds with when the problems began, then the issue could be something Microsoft did in the update. It would be a good idea to check when the web browser(s) was/were last updated and see if the time periods match up with the when the users began having problems.
Different products can use the same shared libraries and encounter similar problems. With this in mind I also suggest searching the internet for similar symptoms with a time period in the past week (or month, etc., whatever makes sense) to see if others are encountering the same or similar problem within their non-Wintegrate product.