Stuck on Loading Dayback

I have an install of DayBack 10.03 (upgraded from 9.81). There are dozens different clients that connect, but most are running FileMaker 14 or 15. There is one machine (running FM15 on Windows) that is getting stuck on the "Loading DayBack" screen. I can't tell where that message is coming from or when in the open process, but the Calendar layout just stays on that message. I can open the status toolbar and navigate to other screens with no problem so the database itself isn't stuck.
Is there something I can check regarding the browser or Internet connection on that machine? Any other reports on this? Thx!
Is there something I can check regarding the browser or Internet connection on that machine? Any other reports on this? Thx!