IDK and there is no way to know for certain, but........
Some laptop keyboards, especially when it comes time to type numbers (as in a "PIN") can behave unexpectedly.
Have you attempted to use the Ease of Access icon on the sign-in screen to bring up the On Screen Keyboard and use that to attempt to enter your "PIN"?
Can you use the "Sign-in Options" link to use your actual password instead of a "PIN" to see if that produces any better results?
On the sign-in screen, does the "Network" icon appear proper or does it have an "X" on it, indicating that there might be a connection problem?