I only have one processor and have no problems. The latest Bonic is 5.8.16 try upgrading.
Forgive me, but since you only have one processor I don't see the relevance of your not having any problems. The 64 bit Boinc I have is the most up-to-date for my distribution and since work units for other projects didn't have this issue, I think it's unlikely that an upgrade would solve the problem.
Also for the last several days all WUs were hanging at the 98% mark (no cpu usage.) I rebooted and now they complete normally.
I mostly don't have any problems running work units. From time to time one unit seems to hog the CPU without appearing to do work (according to BOINC Manager) and in this case I just abort the job and everything returns to normal. Oddly, the symptom of this is that gkrellm shows the job just running on one processor :-( Aaarrrgh.
I guess I'll just detach when the weather gets hot.