System crashes with video web chat

I have a Toshiba A305-S6837. Every time I attempt to video chat online, my entire system crashes and shuts down within 5 minutes or less. I have double/triple-checked my firewall settings, and have deleted and downloaded Skype at least 3 times. So far, I have tried using Skype, Google video chat, and AIM video chat--ALL three cause my system to crash within 5 minutes of establishing a chat session. Any ideas? Very frustrating.