T7500 Workstation Freeze After Start-up, OK After Hard-Shutdown/Restart

This is a strange problem. After start-up, the machine freezes. If I do a hard shut-down and then start-up and never turn it off, it's fine as long as I don't restart or do a soft-shutdown, if I  hibernate it during the good cycle, it won't freeze on wake-up. I've taken out the riser card and all is fine until I put it back in. The memory test showed a problem between the system board memory slot 3 and slot 3 on the riser. I took the memory out of the riser and installed it on the main board with the riser out and all is good. I even flip-flopped the main and riser ram and the problem still persists, so I know it is not the memory modules.

Has anybody had this type of problem?  My first thought is the riser card is bad, but I don't want to spend the big $$$ unless I know for sure that is what it is, or maybe the main-board.

T7500

24 gb ecc ram

dual xeon processors

Windows 8.0 pr0