I see this issue, as well. Was using a Dell Alienware laptop as a development machine. No problems. That machine is about 2 years old. Recently, I built a new mid-tower computer and that's when the problem became apparent. Right-clicking anything causes the application to crash. I believe I've seen the error message that Jason included but usually it just silently closes. The problem computer uses an Intel processor, an ASUS system board and an nVidia G-Force GTX-950 video adapter. I purchased the components about two weeks ago.
When I run pgAdmin III using VirtualBox guest machines there are no issues. Actually, I had a problem with pgAdmin III crashing yesterday but that was after several hours of constant use. I suspect the issue is somehow related to the video drivers. For what it's worth, the system board has an Intel network adapter that isn't fully supported by Linux 4.1.20-11 but I have since installed a WiFi adapter that is fully supported.

On 05/16/2016 05:03 PM, Jason Churcher wrote:
Version 1.20.0 Beta (Aug 10 2015, rev: REL-1_18_0_116-gd491
Running Ubuntu 15.10 64-bit
Installed pgAdmin via Ubuntu Software Center
Steps to recreate:
pgAdmin will force close when:
- Open pgAdmin
- Right click on any of the items in the Object browser
- Do anything
- Select an option from the menu
- Try to navigate off the menu
- Press 'escape'
Additional Info (possibly related/unrelated)

If I click "Stop" pgAdmin will force close, if I click continue pgAdmin stays open.
Steps to recreate:
- Open pgAdmin
- Press the drop down button beside the "Execute last plugin button"

- Error message above is displayed