I upgraded from 11.10 to 12.04 last week and Boinc stopped running instantly. I understand that there is a problem with Boinc and 12.04 -- there seems to be finger pointing in both directions at this point in time. It seems that Boinc is working on a 7.0.27 release and that bug reports have been registered with Launchpad. Not sure where response should be coming from ~~~~~ Boinc still not working!
By the way - I use "seti@home" as my project. 7.0.25 is my current Boinc install.