Eerily similar issue here. I just purchased a new Core 2 Quad Q9300 CPU for my dekstop which has an Intel DQ45CB motherboard in it. Running Windows 7 Ultimate with 4GB RAM. My issue is when I put in the new Core2Quad processor and I enabled the Core Multiplexing option in my Bios my pc will noot boot. I have the most recent Bios update for the DQ45CB(per the processor specs any Bios over 0059 should be fully compatible and im on 0129). If i disable the core multiplexing option, the pc boots fine but will only show the 2 boxes under Performance in Task manager for CPU Usage History so it will not run in "Quad" mode. Has anyone ran across this or have any ideas as to how I can get past this. My Core2Duo runs fine but I'd really like to utilize this new processor with that board! Any help or suggestions would be greatly appreciated.
I have same exact issue I tried different motherboard and different CPU, Hard drive even RAM this is very strange.
Only boots when core Multiplexing is disabled ??!! No answer from intel except your CPU is defective, I tried 3 different Quad cores with same exact issue.
I don't know how to fix this issue <-- have you got any answer?