svchost = Application that works as a host process for services that run from dynamic link libraries.

svchost itself is not harmfull. But when it asks for permission to the net it depends on what is asking. Normally it is ok to allow it, but there are viruses/trojans that are using to svchost process for not so nice reasons. You can use this application to see what modules are used.

And personally I am more thinking of a hardware error you are having. Have you already tested the memory? (memtest86)