Macbook4,1 10.6.8 and firmware update - what went wrong?

Question

Macbook 4,1 2008 2.4Ghz (not unibody). I recently reformatted my hard drive and reinstalled 10.6 from the Retail DVD and all seemed to go well. The MB was working fine up to that point. I then set up the MB (network, date and time, etc.) and repaired permissions.
I then checked Software Update and downloaded and installed the recommended updates to 10.6.8.
Again, all seemed to go fine. System booted and I repaired Permissions again. I went to the Apple web site, a couple of other web sites, and Software Update found another update to install: Firmware. Though I don't remember what version.
I clicked OK and it installed.
Upon reboot, it seemed to install okay.
But then I left the Macbook and it went into Sleep.
I didn't come back to it again until the next day.
When I pressed a key to wake it, I got what I now know is the screen that appears after you wake it from SAFE SLEEP. As per this Apple KB article: http://support.apple.com/kb/HT1757.
And this is where the problems started.
After the MB woke to the Safe Sleep screen, which shows the desktop a little "out of focus", the progress bars started filling in from left to right, BUT before they completed, the screen went BLACK.
And it has had a problem with black screen ever since. I can boot the MB from internal or external HD or from DVD, and it seems to boot fine. Boot chime, Apple logo, spinning wheel, then at the point where it pauses, blue screen, then goes to desktop, instead the screen goes black.
It finishes booting, but seems to go into Sleep.
I can wake it by pressing a key, but the screen either comes on and goes black again after 10 seconds, or I get the Safe Sleep wake screen, and then it goes black after 10 seconds.
And at boot or when waking the MB, the front LED flashes 5 times. There are no error beeps.
I've tried changing RAM, but problems remain.
So what's all this? Any ideas?
The display doesn't seem dead, as it works to boot and wake. The MB works fine with external monitor.
It's weird, but I can't think of anything apart from the Firmware update. The problems started right after installing it.
Unfortunately, this model of Macbook doesn't have a Firmware Restoration image to download and burn to CD. It is the ONLY Mac at this point that doesn't have this!
I called Apple support and even bought the 49 Euro Pay Per Incident service, which proved to be the same as throwing 49 Euro out the window. The only "technical" support they provided was to Reset the SMC, which you can find out about FOR FREE at the Apple website. And which I'd done anyway. I'd also reinstalled the MacOS. Don't want to beef too much, but sheesh, you've already got a Macbook that might need costly repairs, and they make you pay 49 Euro BEFORE they even ask you about the problem and what you've done to try to solve it. I'm tempted to say "ripoff". I mean, if all they can offer you is the advice to reset the SMC - which Apple offers for free at their website - then that's pretty poor service for 49 Euro, to say the least.
Apart from the wasted 49 Euro, I'm pretty peeved about the Firmware update (or so it seems) wrecking a perfectly working 2008 Macbook. I don't know how to convince Apple of this, but I'm certainly going to try.

Answer 1

Thanks for the reply.
Re. the Displays setting, the Macbook display isn't recognized and mirroring isn't an available option.
I've scoured the net and the idea of replacing the PRAM battery may be something to try. I read a post by a guy with a Macbook logic board screwed up by a Firmware update, which he solved by replacing the PRAM battery, as when you disconnect it you reset the logic board.
Which capacitor?
No luck so far with talking to Apple. I will try to get hold of someone a little more tech savvy and/or in a position of authority, as it seems that the Firmware is the culprit. Obviously a million other things could go wrong with a Macbook, but given the timing here it looks like the Firmware. Firmware updates can and occasionally do screw up a computer, as most manufacturers will warn you before you apply the update: PC makers, printer makers, etc. And they probably warn you that it's all your responsibility if anything goes wrong. But re. the Apple Firmware update:
1) it came thru Software Update
2) there was no warning
3) to make things worse, there's no Firmware Restoration image that I can burn to a CD to reflash the logic board: this is the only Apple computer that doesn't have a Firmware Restoration option
I'll try to get thru to a manager and convince him/her that the firmware may have been the cause.
Do you think an authorized Apple tech might have access to some way to do a firmware restoration? Something not avaiable to mere mortals? Because if not, the only solution looks like a new logic board.