It seems like that you are infected with Trojan (can be other things but the first impression is Trojan) Try running Antivirus + Trojan-remover and scan your computer for infected files.....

Other thing can be a virus running on your computer and damaging your system files which is resulting into crazy things.....

If you can elaborate your problem....then we can be in better position to solve your problem.....

When you disconnect your computer from LAN....Do you witness the same problems ?