Weird Dell E310 problem

My son put a new power supply in this pc and all seemed fine. Today while on the PC I put on a windows update. The PC had to restart but would not restart. I had the flashing power switch. I opened it up and started checking to make sure everything was plugged in properly. I took out the front USB panel and was able to restart the PC when pressing the switch on the USB panel. Weird...not done. I reinstalled the USB panel and now was able to restart the PC with the normal switch. When I set the PC back up vertically, it shut off. I got it back horizontal and was able to restart it normally. I shut it off and and was rechecking everything. I noticed that while the PC was on that if I depressed the front USB panel ribbon connector where it plugs into the motherboard, the PC would shut off. I am wondering if the ribbon connector could be bad or maybe the motherboard itself. I cant get the PC to operate in the normal vertical position. Any thoughts are appreciated.