Does anyone know what might be causing these errors?

Notice: Undefined index: httpbl_key in /hsphere/local/home/jessia/web/sites/all/modules/badbehavior/bad-behavior/blackhole.inc.php on line 39 Parse error: syntax error, unexpected T_CONSTANT_ENCAPSED_STRING in /hsphere/local/home/jessia/web/sites/all/modules/notifications/notifications.module on line 1893

Says it's an error with the notifications module, in this instance, but if I disable the notifications module, I get the same "T_CONSTANT_ENCAPSED_STRING" error with a different module and a different line.

It started when I was uploading a work-in-progress website to the server for my client to preview. And I can't say what went wrong from there. I do know that the version of Drupal that I was using to build the site was a more recent version than the one on the server, so I uploaded Drupal 6.20, copied the database over, and tried to update... and I get a 500 Internal Server Error when I try to visit the update page.

I have a multi-site installation and it's affecting all of my websites, including http://www.starpals.org/index.php and http://www.onestar-awb.org/index.php among others.

Can anyone give me some advice? Everything was working fine prior to this, and working fine on my local installation, but somewhere, something went horribly wrong when I tried to transfer it.

-Jessi