thunderbird freezes on launch

[Snowhog]

but i've gotten better and faster answers from this forum than i ever have at the mozilla forums,

Cool. We like hearing that.

[przxqgl]

apparently there was something wrong in the session.json file, because when i renamed the current file and replaced it with the session.json.backup file, the problem went away.

thunderbird 115.6.0 (64-bit)

very weird, but not completely unexpected.

[przxqgl]

i realise this is the mail client, and not the operating system, but i've gotten better and faster answers from this forum than i ever have at the mozilla forums, so bear with me...

kubuntu 22.04
plasma 5.24.7
qt 5.15.3
thunderbird version unknown because it's frozen and i can't do anything with it

before today, i have had no problems with thunderbird. today, every time i launch thunderbird, it starts trying to connect to the ONLY IMAP account i have (i have a number of different POP3 accounts, and it USUALLY checks them first, but not this time), and it gets to the point where it says "connected to mail..." and then it freezes... clicking does nothing, no changing directories or accounts, no menus, no response whatsoever.

i'm at a loss... anybody have a clue? thanks.