What exact version of AE are you using (down to the last decimal point)?
What format and codec is any footage are you using in your scenes?
What other assets are you using?
What third-party plugins?
Heck, we don't even know what the error messages or crash logs say when it goes down!
thanks for responding ..
i uses after effects version 11.04 and i use element 3d that happens when uses metropolitan packs
i tried to exported as Avi 1920 by 1080p and the frame rate is 29.97
and when its crashes a small box appears says after effects is not responding and sometimes the whole windows freezes and i have to take off the bettery to shut it down.
and i forgot to mention that my graphics card crashes too and here a picture of the after effects when my that happens. @Szalam
That bit about the graphics card crashing and that you're using Element 3d are some very significant pieces of information...
Update Element. They released a bug fix update recently.
Update your graphics card driver.
If that doesn't do it, lower the quality settings in Element.