Dell Inspiron 1420 wont post after swapping keyboard

A client of mine needed a battery and a keyboard for her laptop.

After swapping the keyboard and putting everything back together, this is what happens when I press the power button:

The power led turns on, the hard drive led turns on, and the caps lock led starts flashing.
After two seconds, the hard drive led goes out.
The caps lock led continues to flash for a total of 45 times then goes out.
Then the power led goes out.
Nothing else happens - no post, no beeps, nothing on the screen.

After checking and re-checking all the connections, the same thing happens.
Thinking I may have received a bad keyboard, I put the old one back in.
Same result.

What have I done? I know I installed the keyboard correctly - it's something I've done dozens of times.
The inside of the laptop is pretty gunked up. Lots of dust and evidence of spillage.

I'm ready to take the whole thing apart and clean it but I thought I would post here first.
Anyone know what the flashing led means? I have searched the internet and can't find an answer.
I found a couple postings by people with similar issues but with no replies.

Thanks in advance to anyone who can help.

Dell Inspiron 1420 Laptop
Service Tag # C9X2DF1

 

Documentation

There are the Dell documents. Do you get the BIOS to load? You said it is gunked up, is it possible there is some corrosion that was broken when the laptops was taken apart?

 

Thanks for the reply.
I have those docs and some better info I found on the net.

Since my last post, I completely disassembled the laptop and cleaned it, so the gunk is not an issue.
Actually, it wasn't bad inside, just a few sticky spots on the bottom cover.

After re-assembly, I have the same problem.
The caps lock led flashes 45 times and that's it.

I'm guessing the motherboard is dead.