Using any plugin results in http 500 error (and only plugins)

Question

I am working on a site that was previously made by someone else. Whenever I try to use a plugin (eg. Dropbox Backup & Restore, Reset WP) I get an http 500 error.[I made a backup using filezilla.]

using any plugin results in http 500 error (and only plugins)
troubleshooting
-htacces.bak (ftp) x
-PHP memory limit (ftp) x
-faulty plugins x
-permissions for folders (ftp) x
-corrupted core file (ftp) x
-host end issues - contacted

I am at a loss here, and don't know what else to try. Now, it might be a fault on the hosting end, but I would really appreciate some input as to what else might be causing this.

Answer 1

try these : go to dashboard >>updates>> reinstall wordpress

if still does not work rename: plugins folder to "plugins-old" and create new empty plugin folder

if still does not work try changing the theme

let me know how it goes