PSU go BANG. But was it a coincidence?

Hi,
Basically I use home network to connect 2 PC’s. Mine has Norton Anti Virus and Internet Security on which i have to disable when i want to use the network (I disable them because i can’t get the network to work otherwise).
So, i was using the network and then went onto the internet. About 10 minutes in I realised I had not re-enabled the virus protection for the internet. About 2 or 3 seconds after doing this a BANG came from the other room. The PSU on the other PC had burnt out.
Was this a freaky coincidence or has anyone come across something like this before?

Thanks, hope you can help.
Adam