Re: Problem deactivating plugin
For the first error, I think in 0.8.3.1 it is looking for an underscore plugin, but you have none in the plugin folder any more, and it errors out.
This is line 169 from bb-settings.php:
foreach ( glob(BBPLUGINDIR . '_*.php') as $_plugin )
I would create a blank php file called _nothing.php (nothing in the file at all) and put that in your plugin directory. The name of the file does not matter, except it needs to begin with an underscore. The contents of the file don’t matter either. We just want something for bbPress to see in that directory so it does not fail. That should prevent the first error. I think it will actually take care of the second error as well. It’s also related to having no underscore plugins in the plugin directory.
Thanks for posting your bbPress versions: it was invaluable in finding the right line numbers and relevant code.