Cubase 5 crash really often (macbook pro)

i know a lot of ppl have this problem - but i didnt find answer for mac.

my cubase crashing really often - every 15 min
most of the crashes happens when im using Amplitube 3

i have cubase 5.5.3
2.2 ghZ i7
8 GB 1333 MHz DDR3

tnx for the help!