Many computer and network problems (not able to access websites, computer running slow or crashing) are actually caused by either malicious programs that can infect your computer when you browse the internet or by registry corruption than can be caused by many different factors.

You can see if your computer and network are affected by any of these problems by scanning your computer with latest antivirus and anti-malware tool.

Also some browser toolbars may interfere with your access to router or modem configuration tools. These errors also could be fixed by anti-malware tools.