Thank you for your post.
It's difficult to determine what is the cause, but my first instinct is that it is a corrupt database. To test out this theory, create a new database file with one field and one record. Turn on Instant Web Publishing and set web access for this file to "All users". Go to another machine, launch the browser and see if you are able to see the database file and access it. If so, without any freezing, then the original database file may be corrupt.
If freezing occurs with the new file, then it is a good assumption that all files are fine but either FileMaker Pro or the OS is causing a problem. Since you just installed new Windows update yesterday, it seems a likely culprit, but that is a last resort since I know how much of a hassle it is to reinstall an OS. I can't determine if you are running FileMaker Pro or FileMaker Server. In either case, uninstall and reinstall FileMaker Pro/Server. Once everything is installed, launch FileMaker Pro/Server, and then see if you are able to access the file remotely (via Instant Web Publishing or FileMaker Sharing).
Let me know what else you have tried short of reinstalling the OS.