I just purchased a TYAN S1854 Trinity 400 rev 1.07 as a replacement board for an older system. I transfer the old parts over to the new board without any trouble. The problem arises immeadiately after the system posts. After the post my display comes on, and shows me my processor and ram speeds along with the total ram installed on the machine, by this time the machine is completely frozen. Due to this immediate freeze I can't access the bios to tweak the settings. I have tried using different ram but have the same problem. I've also checked the jumpers on the board to make sure there were no conflicts regarding bus speeds.
Forum has been up quite a while. From my own experience it's a great mobo and has been in constant use for 20 months now.
In your manual there is a jumper to reset cmos to defaults and try reseating the dimms (it's the #1 cause of problems).