If you have read http://www.blackberryforums.com/gene...ee-memory.html
and followed the advice there, then you know the score.
You might take a look at your message options and see how long the BB is set to keep messages. If you receive a ton of email and you have it set to keep forever, reset it to something like 30 days.
Other than that, you need to delete some apps. Get yourself up to about 10-12MB free after a hard reset.
With only 64MB and the newest operating systems, you don't have a lot of room left. Be judicious about what you install.