Differences in Java performance under OS 10.6 and 10.5

[Chris Crawford]

I've been developing my program on a machine with OS 10.6.8 and everything is going very well. However, when I tested it on a machine with OS 10.5 (and another one with OS 10.4), I got consistent failures to read in image data during program initialization. The older machine fails to load all the images and then can't display them. I checked performance with Activity Monitor and discovered that the OS 10.6 machine was using 185 MB of real memory and 401 MB of virtual memory. The OS 10.4.11 machine that I tested on showed only 96 MB of real memory usage and 385 MB of virtual memory usage -- and 577 MB of free RAM!

Why does the older system fail to allocate enough RAM to handle the program?
What can I do to fix the problem (other than load images only as they are needed)?

Thanks for any advice.