What happens if you temporarily go back to running 100%? Does it start up like normal? And then try switching back to 50%. So, is this reproducible?

What version of BOINC are you using? This used to be a problem around 5.7.? (I don't remember what version the bug got fixed in, but I was the one who reported the problem initially).

I saw on the Rosetta forums last night that WUs mysteriously stopping seems to be a new bug introduced with the last update of the science app. Most reports (if I'm remembering right) were on Macs. So what OS are you using?

What happens if you temporarily attach to another project? Do you see the same behavior.

I'm trying to narrow it down to a problem with Rosetta or a problem with the core client.

I have a Mac OS 10.4.9 dual 2 GHz PPC G5 with 2.512 GB DDR SDRAM running Boinc v 5.8.15. I run at full 100% cpu all the time but have recently had Rosetta tasks that hang. They generally will not start again even by 'suspending' the taks and 'resuming' the task. I have shut down Boinc and restarted Boinc which will usually correct this kind of a problem. This past two days the tasks stay in memory but doing no work and the only way to get going is to Abort the task. Boinc reports the jobs are running when they are not.

I post this to help address the last question you have. I have other tasks from other Projects running and they are still operational except when Rosetta tasks stop, Boinc considers them running and will not allow another task to start. I have seen holds like this up to 10 hours in the past few days.

Hope this comment helps you.