To be honest, if you can't immediately say yes it's that (and only that) cheap part
Like just the pololu driver, or just the regulator, just the mcu or just a trace on the board then I'd just throw away the sanguinolu and go with ramps. Or the x3, (or there is another board mentioned in a new thread that's much more featured than the stock board.

Solidoodle was not offering replacement boards on their site when mine died though I see they are now.  (edit: To be clear, I should say when I killed it.  It was not defective.)

I am very frustrated with Solidoodle "support" right now and wish I had the email addresses to Solidoodle management.

Solidoodle support and management often read these postings, and occasionally respond.

I think that I am going to try to put an new 5v reg on the board, some new motor drivers, and try it all again.

If I blow the motor drivers again WITH the 5v reg on the board, then I guess I will have to wait for my "expedited" replacement motherboard to come in.

I am very frustrated with Solidoodle "support" right now and wish I had the email addresses to Solidoodle management.

Thanks!

it'd depend how the 5v reg failed.

Certainly my 5v reg failed and had the same flashing lights symptoms. I figured this was the failed part, read that it wasn't needed and just cut it off, and have been printing happily ever since.

If your failed, (like my did) but failed in a different way that may have caused your motor driver issues.

Two further questions/things to try.

try removing all your motor drivers, and then try turning the machine on. does it still flash etc.

second, with the 12 brick not plugged in, but with the USB cable plugged in, is the redlight on the board on?

Yes, I completely removed the 5V regulator.  I am wondering though if because that regulator is gone, it may have caused these motor drivers to fry.

Here is a photo of one of my fried motor controllers.

Thats crazy. Did it ship this way or did you actually witness it "fry"?

First, I ordered a brand-new full "motherboard" set and was in contact with support and told them that I needed it expedited and shipped overnight to me, I would pay the cost.

The support person said that they would expedite the order.

The site said the boards were in-stock, so I would have expected it to ship on Monday.

My order still says "pending", and support is no longer answering me email asking about status.  They only answered when I was about to put in the order.

NOW, I ordered some brand-new Pololu md09b stepper motor driver boards.  (directly from Pololu, and they arrived when they said they would).

I put the boards onto the motherboard, tuned them to the exact proper voltage...

Plugged in my power-supply, and the whole power supply started flashing on-and-off.

So, I scrapped the crappy Solidoodle power supply and used a computer power supply.  (no more power regulator on the motherboard either)...

Everything seemed to power on just fine, so I hook it to my computer, same "over powered USB device" message.

CRAP!

I start looking over the motherboard, again, with a magnifying glass.  Both the Extruder and the Z-Axis pololu boards have fried, there are holes in their controller chips!

CRAP! CRAP!

Now I really have to wait for my replacement motherboard because it seems like something is seriously wrong with this one!

God only knows when Solidoodle will "expedite" my replacement to me.

</rant>

This happened to my printer. If you always print from a pc the 5v regulator just isn't needed.

When all are removed, I get the solid red light on my board and my Mac sees it as a valid USB connection.

If I connect #1 or #4 (doesn't matter in which position), I get no light or a dim blinking light, and the "too much power" message on my computer.

If I connect #3, it is a solid, dim light, and sometimes it gives me the "too much power" message, sometimes it does not.

It just seems very strange that 3 of these little boards would fry all at once, but right now, that it what it is looking like.

Any other ideas?

(oh, also new USB cable tried).

Thanks!

Thanks.  I will see if I can find anything.

All of the socket stepper drivers use 5v, you could try removing those.
If your endstops and thermistors are disconnected, it can't be those.
That leaves the FTDI chip (USB to Serial) and the PCB traces themselves.