Hi, i have the same problem as BAM. Using a Asus a7N8X-E deluxe mainboard
HWID:
PCI\VEN_1095&DEV_3112&SUBSYS_61121095&REV_02\4&3B1D9AB8&0&5840: Silicon Image SiI 3112 SATARaid Controller
Problem: not the sil3112r but the sil3112 file is loaded. IT HAS TO BE sil3112r!
This problem only occurs when using hdd's in RAID. (With non-RAID the si3112 gets loaded offcourse, and install works perfectly)
I tried an normal windows xp pro with sp2, loaded the (newest) sil3112r drivers via f6, and it worked.... So its not a driver problem.... :S
I hope you can do something with this info Bâshrat.... 
Good luck!