It is possible to switch to Apple system dialogs in the advanced settings. The default look that you see is set because some users reported problems. The Apple dialogs may be fine if you have a more modern system.
We have many thousands of users who run AC3D every day so it really shouldn't be crashing for you.
Please contact us (
http://www.inivis.com/contact.html) with more details on the crashes, if you can duplicate them, please include the operations you did and save any files that caused problems.