One of our clients uses a Java-based financial app that loads from a web page. As part of resolving another issue, I removed and reinstalled Java from the workstation. It never occurred to me that I should test the financial app because it had not given me problems in the past when I applied updates. Also, I don't have a logon for that app because it would give me access to the data related to their customers.
Anyway, on Monday morning I get a polite call telling me that the app is not working. This app requires the user to accept a certificate from the vendor the first time it is run, and I assumed that the user accidentally said no to accepting it. So, I took remote control and it definitely did not work. The error, complained about security in a roundabout and cryptic way.
After some testing and tweaking, no fix. Later when doing some research (ok, Google searches) I found out that this is a bug in the last two releases of Java for apps with certain characteristics. I had installed Java 6 update 16. The last version without the bug was Java 6 update 14. Remove the new version, install the old and all was fine. Fortunately all the older versions of java are archived and easily available.