RDM Remote Desktop for Mobiles 4.2.5
the author of this app says:
Access remotely your computer even through NAT and Firewall from mobile. You can send and receive emails, edit word documents, surf web, manage files and folders and do hundreds other things that you usually do sitting in front of your home or office computer.
BlackBerry OS 4.3 or higher. See homepage for other BlackBerry supported versions.