|I strongly suggest to scan your laptop for viruses and trojans.|
Windows gets stressed, when a program or service tries to access a network or the internet, and it's impossible because of any unavailability.
A well programmed software will give up after a timeout, but a virus is not part of well programmed software.
I suggest to use a bootable Antivirus Rescue CD.
The advantage is, that windows did not run at this time and also a virus did not run at this time, that might try to avoid virus scanning.
An already installed Antivirus software may possibly be infected too.
So e.g. go here:
download and burn Avira AntiVir Rescue System:
Start your laptop from this CD, click the update button, change the settings, if needed, and start scanning.