Hello from the world of tomorrow!!!! ... google result #2 for the phrase "M4A89GTO freezes".
This motherboard is designed with a small insert card that must go into PCIE_0, the top slot closest to the CPU if you are running in a single GPU configuration. Your video card only works in the bottom slot because it's designed to be done that way.
Read the manual. Seriously, It's right there. In Chinese-almost-English.
PS. If you don't have the small insert card your second slot will only ever hit x8, never x16.http://forums.xkcd.com/viewtopic.php?f=7&t=76560&sid=79bfa8ae6fa1e89423fd33c663537da2