A few things to look at and a few questions to ask:
First, What OS, installed Ram, and what Processor are you running?
Second, why 1440 X ? (this is a non square pixel width project if its 1440 X 1080) The only format that will playback without distortion would be DVCPro HD. If it were my project I'd be working 1920 X 1080 unless there was a very compelling reason to do otherwise.
Third, when you say very high rez 3D layer what do you mean? Only the pixel dimensions matter. Since it's a 3D layer it should be scaled to 100% and at some point in your project the distance between the camera and the high rez still should be somewhere close to the same value as the Zoom value of the camera. IOW, look at this screenshot:
The camera is centered in the world and at 100 pixels in Z, the high rez layer is centered in the world and at 950 in Z, the difference is 850 pixels, the zoom value is 847 pixels, therefore the layer is at approximately 100% scale, is going to look as good as it can look, and no matter what the pixel dimensions are, it's the right size for the composition.
If the high rez layer were closer than the zoom value the effective scale would be higher than 100% and the image would not contain enough pixels. If the high rez layer never got any closer than 2 or 3 times the zoom value (1600 pixels) then the image is too big. This could be causing your crash.
The last thing you should check are the Secret preferences. You find them by going to Preferences>General and holding down the shift key while you click. This will reveal the Disable Layer Cache and Purge settings. Try purging every 2 or 3 frames.
Last of all, AME CS5 should import a JPEG image sequences just fine according to the Docs. It's easy to give it a try. I've never tried myself. CS5.5 should import any type of image sequence. You can also import your AE project directly.
One other thing, you can also pick up an animation codec qt after a crash as well as a photoJpg QT. The movies will be in tact, it's just a little harder to pick up the right frame number.
Could be a bug, could be soemthing to do with temporal magic. Impossible to tell. You could always try a third-party ripple effect or rebuild the ripple with teh normal displacement map effect. Also with regards to the layer do the usual of pre-composing. Maybe it avoiuds the issue...