Server Trouble

I've been away from the project for a while, so I decided to switch my files over last weekend. I started by copying the photos (15GB). About 10 minutes into the copy, an error box popped up stating that the server could not be found. The PuTTY session that I had opened failed at the same time. Thinking it was a fluke, I reconnected and tried again. Same thing. The next day (after restarting the server) I tried some different files. Still, it failed.

I'm not sure what to do next. I'm no expert on hardware, but I may see if I have an extra network card to swap with the current one. My daughter used this computer for a couple of years without incident, but she never tried copying gigs of files in one sitting.

We'll see.