Suddenly, I have this persistent fault: When I open Thunderbird in Gloria, only the very top bar appears, with an outline of the window within which is part of the desktop. I can drag it around by a mouse pointer in the top bar, and the whole of that part of the desktop moves around with it.
This happens whether I open TB using the icon on my desktop, or from MintMenu. (The icon was originally dragged from MintMenu).
Firefox has also become somewhat slow to open or respond to some GUI operations. (2nd edit): This too quite often 'hesitates' for a while with an empty windowframe under the black Firefox header bar. THat's why I wonder whether there might be a hardware cause.
Gparted shows me that my /home partition of 15.83 GiB has 13.52 GiB unused. The root partition also has plenty of unused space. These are in the extended second partition of hd2 which is a 500 GiB SATA disc. The MBR is on hd0 which is an 80 GiB IDE disc.
The fault has sometimes recently occurred briefly, with the normal window of Local Folders appearing after slight delay, but has now become persistent. This is after successful use during most of the present session.
Now I have carefully shut down and rebooted - the behaviour of Thunderbird is unchanged.
1st Edit: After about an hour, TB has successfuly opened. What's behind this behaviour?