FB2 eats up a lot of memory because, well, it simply eats up
a lot of memory. Tis the nature of the beast. On my machine, it can
easily go over 400MB. If you read Adobe's system requirements, I
believe they state that you should have at least 1GB of RAM.
They're not kidding. I have 768MB and FB2 performs reasonably
One other thing to check is which JRE you're using. I was
originally running on 1.4_10, and my memory consumption was in the
700,000k range for javaw. I upgraded to 1.5, and it's brought it
down to a more reasonable range.