Today I changed around my antenna set-up slightly and since the changes I haven't been able to transmit on 20 or 40 meters for more than couple of seconds without my computer shutting off.

I'm restricted on antennas so I have to use the aluminum rain gutters as the antenna. It's basically a dipole but made out of the gutters.
Before I just had the coax connected to the gutters. Now I have a 10 foot run of rg-8 from the tuner to the 4:1 balun that I have outside. From the balun I have a 10 or 15 foot run of 300 ohm twinlead that is connected to gutters.

Does anyone have any ideas on things that I could do to help prevent this from happening? I do all my logging on the computer and my primary operating mode is PSK31.

Thanks,
Tim
KC9FSH