What are you applying the Puppet Tool to? A PNG, a JPEG, an AVI? What size is it? What size is your comp?
What exact version number of AE are you using (10.5.____)?
7GB of RAM? That's odd. Wouldn't it be just crazy if the unusual RAM configuration is causing this?
its a shape layer rectangle for a leg or an arm. Comp size 1920x1080. AE version 10.5.0.253. It would be nice and convenient it the ram was the cause.
Well, you could update: After Effects CS5.5 (10.5.1) update
However, I doubt that's your issue as the bugs it fixes seem unrelated. Try precomposing those shape layers and applying the puppet tool to the precomp.
Well I turned off my computer and started it again with a shape layer then turned to a pre comp and so far its working. but i tried it the original way again and its still working with no crashing. I even increased the mesh to a 1000 with four starch points and its still working. Only thing is that is really sluggish to adjust to points position and looks like its about to crash but doesn't. Sometimes the points done even move. Could that be the lack of RAM or processor speed (2 x 2.66 GHz Dual-Core Intel Xeon)