[PD] Cannot change blocksize (Mac OS X)

I cannot set the audio blocksize of Pure Data. It defaults to 64, which works.

If I open the settings and change it to e.g. 256, pressing save does nothing, and I cannot close the window and have to force-quite Pd.

I am running Pd-0.47-1 on OS X 10.11.5 on a Macbook. I have tried both the 64 bit and 32 bit versions of Pd. No libraries installed.

I have also tried running Pd from command line with option -blocksize 256, in which case Pd does not start (the icon just jumps up and down in the launch bar).

I have also tried changing the default value of 64 to 256 in the .plist file. Pd does boot in this case, but if I enable DSP, it stops responding.

I was asked in the Pd forums to try this mailing list.

Any hints?

Thanks, Mikkel Gravgaard