pan won't connect, and when I try to close it, it won't close.
gkrellm shows outgoing spikes, but almost nothing comes back
Removing it and re-installing makes no change in behaviour.

What to do?

I assume that you have verified the server URL and user password.

To close it, you could run

from the command line, find the process number, then issue

from the command line. Sometimes it can take a moment for the process to die.

I would suggest then starting pan from the command line; it might output errors to the terminal that would be useful in troubleshooting. Post the errors, if any, here, making sure to enclose them in "code" tags, which become available when you click "Go Advanced" down there at the bottom of the Quick Reply window.

I used pgrep pan, then kill. during this, the taskbar disappeared and on reboot /dev/sda1 showed errors so I had to re-install slackware. This has been happening due to power failures since the big snow before Christmas.

Starting pan from cli shows the same behaviour, but no errors.

Drat. Power failures to a running computer can cause issues.

I've used Pan for years without encountering any problems that were not of my own making (usernames, passwords, URLs) so, without error messages to the GUI or the terminal, I'm fresh out of ideas.