I am guessing by latest version of DM... you mean DM 4.7. It is OK to use this version as long as you do not want to try out beta versions of the OS. Get the latest version of OS at General 8300 Series Discussion - Curve - BlackBerryForums.com : Your Number One BlackBerry Community
and try installing it on your device.
You may also want to try out http://www.blackberryforums.com/gene...ee-memory.html