Is it a Classic or a Rosetta?
If a Rosetta, then the main Wifi is integral and the dongle is for iGRid.
If the other USB device, the SDR, is getting hot, switch off, unplug it and start without it.
Same with the GPS.
One solution to try after all the ones above is to get another SD card, put a fresh version of the operating system on it and reinstall.
Keep the original card safe in case this is not the answer.