PhpStorm 10.0 - add to favorites no longer works

I've been using multiple sets of favorites in my previous version of PHPS, 9.0.2.

After installing the 32-bit version of PHPS 10.0 (build #PS-143.381) the sets of favorites I created previously are visible, with the expected contents, however I can't add any more files to them, or to a new favorites group.

As I rely on the favorites lists quite a lot, I've reverted to 9.0.2.

I've been using the 32-bit version of PHPS on this & all previous versions, as it seems to be more stable in my PC environment.

Platform: Windows 7 Professional 64-bit
8 GB RAM

Thanks in anticipation for any suggestions/fixes.