Help! My site keeps crashing!

We run a Bollywood website called koimoi.com which means we are an image heavy site with plenty of articles and images, embedded games and plenty of videos.

When did we start with wordpress:
On the 15th Feb, 2010 and full fledged (after changing/customising the theme, etc) on the 25th March, 2010.

What exactly did we do:
We started with wordpress.com , then moved to org. We were hosted on Bluehost.

Problems: Site kept going down a couple of times, then Bluehost suffered the DOS attack when we had to move. We decided to move to amazon.

Hosted on EC2, US West –
Problems: Site was/is taking TOO LONG to load.

Our solution: Implementing load balancers (again still using ec2).
Site went down thrice in one day, and went down again the day after that, since we weren’t on a support plan, we couldn’t ask anyone about the problem or the solution.

We are now shifting that instance to another in the Asia Pacific zone. (Our plan is to monitor how the site runs on this instance and see to it that the site is stable for at least 15 days before we do any further modification.)

The site still goes down without warning (the error message reads: error in connecting to db) and we cant get to the controls to restart the instance.

We are still trying to figure out whether the site going down is a network issue or it is due to a setup / configuration error on our side.

It would be great if you could share your thoughts and recommend some solution on the issues above.