Illustrator CS5 Verison 15.1 on a MacBook Pro Retina, 15-inch, Early 2013 Processor 2.7 GHz Intel Core i7, Memory 16 GB 1600 MHz DDR3,
Graphics NVIDIA GeForce GT 650M 1024 MB. Illustrator opens .ai and .pdf files. When I try to open a .dwg file, I get the following message, “The operation cannot complete because there isn’t enough memory (RAM) available”. I have been using the program for some time to successfully open .dwg files. This is a recent occurrence and I have not made any changes to the hard drive other than installing OS 10.9
Have you already opened that specific file at some former time?
Have you already tried a restart?
Apart from that:
Illustrator CS5 cannot use more than 3 GB of RAM, no matter how much is installed. OS 10.9 causes all kinds of problem even with newer versions of Illustrator.
You can try. But then use Jacobs technique: