Euro symbol on keyboard refuses to work

The problem was caused by a telephony client application running on the same computer. I didn't think it could be an issue until I called the client to troubleshoot the issue.

When I asked him to try to type the Euro symbol, suddenly our call ended. When it happened again, I assumed we're on to something.

Sorry for the localized screenshot. The highlighted part says End call:

I don't have a keyboard to test this on, but perhaps your keyboard is faulty or that Windows is not reading the key code properly for that key combination. Try downloading a keyboard tester program like this one and seeing if it detects that key combination, and what code the keyboard is returning. Compare it with a setup that you know works, and see if there's any difference.