I started using 4.3 last night and have run into a couple of
crashes and one case where it hung and I had to kill it
through the Task Manager.
The first time it died, I wasn't paying attention, so I'm not sure
what was the cause. The second time, though, I figured out the what
happened and can repeat it. If you scroll all the way to the bottom
of either the Web Page or Header filters lists, there is a strip
of grey below the very last entry. I was trying to unselect the
last filter entry and clicked a bit too low in the dark grey area
below the checkbox. That killed Proxomitron.
I managed to hang 4.3 twice in the same manner, so this may also
be repeatable. I was switching between configuration files and
had selected File/Load Config File and clicked to open the new Config
file I wanted to load. I hadn't noticed, but there was one active
connection, and I got the warning dialogue with the Retry, Kill
Connections options. It didn't seem like there was any good reason
for there to be an active connection, so I selected the kill
connections option. At that point it completely froze. It wasn't
taking up any CPU time, but there was nothing I could do other
than kill it through the Task Manager.
Other than these problems (which can easily be avoided) I haven't
run into anything else.