Apparently, I'm having a similar issue. My new furnace was just installed a couple of months ago and worked great until today. We're sitting here watching TV and all of a sudden there's a loud buzzing sound for about 3 seconds. I'm like, wtf? At the time, the furnace wasn't running. I went over and pushed the thermostat up and it didn't do anything. I reset it, and it still wouldn't do anything. I checked the power supply and it wasn't making the slight hum it usually does, so I checked the fuse and it was okay. I pulled it apart to see if there was internal fuse. Sure enough, there was, and it was blown.
Not having the proper replacement fuse handy, I disconnected the power supply and connected another one I had lying around. This time when I pushed the thermostat up, the furnace made a brief horrible grinding noise so I killed the power.
I hope like hell that it's only a loose blower fan. Do I have to pull the furnace out/disassemble it to get to the fan set screws? I'll definitely be using some loctite on the screws if that is what the issue is.