No video on power-up odd workaround

[mlpmail]

MacPro 3Ghzx4 Mac OS X 10.5.6 (9G55)RadeonX1900 Cinema HD 30" and Apple Cinema 20".

When I power-on I get no video, computer boots ok, just no video.

Problem started when missing-sync locked up computer.

I have reset SMC and PRAM, did not help.

By trial and error I have discovered if I boot the computer then put to sleep via power button, then swap the ports my two displays are connected to while sleeping, when I wake up computer both displays are working. the primary display has the wrong background. once I have done this I can swap displays back and they still work. If I do a reboot everything works fine even the background is fixed. If I power off computer problem starts all over again.

I have removed and reseated all cards and memory. I have tried to update the SMC and the firmware, but since I am current it will not allow me to reload firmware or smc. Is there someway to force a firmware-SMC update in case they are corrupt?

Any other suggestions of things to try?

Thanks Mike

[cal6n]

I assume you've tried a PRAM reset (http://support.apple.com/kb/HT1379).

Have you tried reinstalling 10.5.6 from the combo update (http://www.apple.com/downloads/macosx/apple/macosx_updates/macosx1056comboupdate.html)? I find that can solve a multitude of issues.

[mlpmail]

You are right it was a PRAM reset and not a NVRAM. I have not tried reinstalling OSX, as the problem happens before drives are even accessed, which is why I am thinking it is a firmware or SMC issue. Problem also occurs on two different OSX installs, one RAID and one non RAID.