Site broken – Error logs indicate Collapse O Matic problem

My site has started giving the white screen of death. The error logs are full of lines like this:

[03-Apr-2015 11:29:39 UTC] PHP Warning: Cannot modify header information – headers already sent by (output started at /home/cohenlaw/public_html/wp-content/plugins/jquery-collapse-o-matic/collapse-o-matic.php:1) in /home/cohenlaw/public_html/wp-login.php on line 424

The part after “in /home….” changes but they are all the same until that point. I can’t log in as I still get the white screen of death on the wp-admin page, but I’ve disabled the plugin via ftp and still have the problem.

Steps I’ve taken:
I tried disabling the plugins and the theme via ftp and still got nothing.
I deleted and replaced my .htaccess file.
I restored a db backup from a week ago when the site was working.

None of these things helped. So I contacted the host and they removed the theme and the plugins through the database. This solved the problem, but of course destroyed our custom site. So I started reactivating things and once again have the white screen of death.

On a whim I set up a new site and imported the database. Note that I have NOT imported the wp-content folder, so there are no custom themes or plugins running. After importing the database the new site started giving the white screen of death.

This makes me think that perhaps there is some stored info in the database that is the problem. Does Collapse-O-Matic store data in the database? If so, where? My goal is to erradicate all data associated with the plugin and see if that helps.

If anyone has a better idea I’m all ears.

https://www.ads-software.com/plugins/jquery-collapse-o-matic/