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Hi,

AutoCAD LT 2013 is not compatible with Yosemite. In fact it could work if you upgrade your OS with AutoCAD already installed, but in some cases it can stop to work, for example after a crash.

You can try to reinstall AutoCAD on Boss's Mac, but I'm not sure that you will be able to run AutoCAD installer (as I say 2013 version officially not supported).

Maxim