I have two systems (H8DGU-F with 847A-R1400UB) have some problem as following.
The first H8DGU-F I used was shipped from you with bios 1.0a on the motherboard and everything worked fine. I noticed that you had bios 1.0b on the website, so I updated the motherboard to have bios 1.0b. After updating the bios to 1.0b suddenly none of the add-on cards posted. So naturally I downgraded to bios 1.0a again and everything worked again.
Please check your BIOS setting when you finish the BIOS flash . Advanced --> advanced chipset control --> north bridge configuration --> slot SXB1 width --> X8 X8 (depend on how many slots on riser card)
Also please update the IPMI firmware to 211 version