Quickproof issues

Thank you Phase One for bringing back the Quickproof function. Having to generate a web contact sheet just to get a bunch of small jpegs very quickly was an annoying process.

Anyway I'm having a couple issues and I wonder if others are experiencing the same.
Several times when processing quickproofs I have received the message:
"The Application ImgCoreProcess quit unexpectedly." This causes the queue to stop and forces a restart of the application, sometimes a system reboot.
I have been able to repeat this crash by processing a set of QP's, then in C1 preferences Reducing the size of the preview, and trying to process again. This consistently causes this problem. There may be other ways to cause this, but this is the most reliable.

I am using C1 Pro 5.0.1 on 3 different machines, Mac Pro 10.5.8, Mac Pro 10.6.2 and Mac book Pro 10.5.8 all have same problem. P30+, Canon 1Ds Mark III, 5D Mark II.

Also I wonder why the 'quality' slider is locked at 90 and the Scale is locked at 100%.
I know that the size of the QP is determined by the Preview Image Size in C1 Preferences, though I'd like to produce Quickproof jpegs at given resolution, but with more compression than 90 to make smaller files for faster uploading. At the moment I am running these through a Photoshop script to compress them further (an annoying extra step). Processing using the regular jpeg setting gives the full size/compression functionality, but it is so much slower than quickproofs.
Any ideas?

Thanks,
Daniel