I am running BOINC 7.0.31 on Mac OSX 10.8.2 on a Mac Pro 2x2.93 Quad Core and have been running BOINC for years.
I came home from work today and found that instead of running 16 tasks it had reduced this down to 8.
In addition it states "Waiting for shared memory"
I am currently running SZTAKI desktop

Any clues what might be going on?

Check the propeties for the work units and see how much memory they need; in addition to free CPU cores, you also need enough RAM available for the WUs to run.

This happened to me several weeks ago: one project was giving me WUs that needed 9 GB of RAM, which limited the maximum number of work units I could run at once.

(I'm using Windows PCs, but I'm sure the same thing applies on a Mac.)

I do have 32 gb RAM so that should be enough.

What I did was abort the forthcoming work on SZTAKI, switched on 'don't get new tasks' and let it run something else, which it then did.

Thanks for your reply

I do have 32 gb RAM so that should be enough.

Apologies if I sound picky, but did you actually check the RAM required for the workunits?

Reason I'm asking: I also have 32 GB of RAM and, as I fouond out not too long ago, that is not always enough. Running three work unites that each needed 9 GB of memory didn't leave BOINC enough available RAM to run any other workunits, even though I normally give BOINC enough cores to run eight WUSs at once.