I have the same issue. It is predominantly when I use Chrome: When saving a file Chrome will lock up and I have to kill the openAndSavePanelService process in activity Monitor to be able to gain control back of the GUI.
I note that if I try to change / close tabs or carry out other actions whilst chrome is locked up when I kill the openAndSavePanelService process, these actions are carried out.
In addition to this I also note that within Activity Monitor there are many other openAndSavePanelService processes still active for other programs. It very much looks like a memory leak issue. I believe these processes should be cleared down once the save action has been completed.
I also believe that as a result of this, control is not being passed back to the app, which in the case of Chrome locks the app up. This response is different in other apps - depending on how they interact with the openAndSavePanelService dialog. For example in ArduinoPro IDE the application functions as normal but no further save actions are carried out. I just lost a days work as a result of this.
So this appears to be a common issue and directly related to the openAndSavePanelService / dialog. There is plenty of internet evidence that many others are experiencing this same issue. Clearly there is a problem.
Restarting / closing / opening apps / Resetting PRAM / using safe mode / creating alternate accounts / etc / whatever, do not solve this issue.
We need a permanent solution
C'mon apple pull your finger out and fix this.