The cake is a lie.
The particle engine is a nice idea but it made my PC lag. A lot. It's not a real good PC (2.2ghz dualcore/Geforce8600) but it should run any "e-card" at a decent frame rate, shouldn't it? Rework that please. Also, the fireworks looked way too static in my opinion.
The rest of it was pretty dull. Text was uninspired, the random font mess is no pleasure to watch and the background music is boring.
If you decide to rework this flash, make sure the text art has some concept to it. You should also consider using a higher quality background music and some more dynamic particles.