Try running your motherboard out of the new case to see if the same error pops up? (use a static mat or provide a static-free environment for the motherboard to run on.) You can leave the case fan attached, but remove it from your new case and let it run unattended.
What happens? (My guess is you may not have taken precautions against static electricity discharge when moving your motherboard over.)
I am currently having an issue with my computer. I just moved the components of my Dell Inspiron 620 (2320) into a Raidmax Super Viper that included a new power supply (500 watts) and 2 fans. We didn't unplug much, and basically just picked up the components of my old computer and put it into the case. The fan on the motherboard was not altered in any way. After much work, we got it to work and the first thing that pops up is a message saying system fan error. I tried download the BIOS update for my motherboard and that didn't work. I checked the cords and as far as I can tell, they are all correct. I ran a diagnostics on the computer and got this error code: 2000-0511.
I am just irritated beyond belief and if anyone has any suggestions, I would greatly appreciate them.
*Note: I am some what tech savvy, but am still learning. If any of the information above is useless I am sorry. And if any information is needed, please let me know.