I use Ubuntu 11.04 64-bit and yesterday I noticed my client report in the messages tab that a new version of Boinc was available. It was released back on July 28 but I never noticed. I removed the old Boinc folder including the hidden file under /home. I installed the newer version but it would not execute, seems that the newer version requires some dependencies not installed by default on Ubuntu. So if trying to upgrade make sure you have these installed first. Can be found in Synaptic.
libcurl3
libwxgtk2.8-0
libbase2.8-0