You could edit CaveRenderPro.bat to increase Heap-Memory to 4 or 6 GB and run this batch file. In my environment with 2GB it prints one page at max. 400 dpi, with 6GB it prints 4 pages at 600dpi.

java -Xms1g -Xmx2g -Dprism.targetvram=1g -Dprism.maxvram=2g -Dprism.vsync=false -jar CaveRenderPro.jar
-->
java -Xms1g -Xmx4g -Dprism.targetvram=1g -Dprism.maxvram=2g -Dprism.vsync=false -jar CaveRenderPro.jar

Thanks for your feedback