When I first set up all my new parts the motherbpoard wouldn't post and the CMOS needed to be reset every time. I tracked it down to only happening when my IDE DVD Drive was connected.
After a great deal of searching on the net using Asus Express Gate's browser I discovered this to be a common problem with this M/B, but I found a single post saying that IDE drives often clash with Express Gate, and to disable Express Gate in the BIOS. Once I did this the system works perfectly with the IDE DVD drive attached.
Hopefully Asus will fix this in the near future as there are a lot of people who still have older IDE drives.