What happens to the hard disk and hd light on the front of the case when you turn it on? If the case is open, you can hear the hd ticking quite loudly as it's being read. When you say the screen is white, are you sure this is the output from the Amiga? I plugged it into our Sony Trinitron to take the vid on YouTube and found I could only plug it into socket AV1 on the TV to get it to display, AV2 did nothing which is really odd.
If the Blizzard board was rattling in the case it's possible it's knocked one of the chips, or maybe hit one of the wires/solder points to the keyboard connector.
If you have a camera can you please take some high res pictures of the board and the inside of the case, specifically the motherboard and the connectors/leads out to the different devices, see if we can see anything damaged or loose somewhere.