Getting permission errors!

Hello,
I have a blog that was doing good until I installed the plugin “buddypress” after a short time I wanted to remove it, but when i tried to delete it it gave me errors. I backed up my database with pressbackup and reinstalled wordpress. now when I try to repair my site using pressbackup again it says i do not have permission. an the same thing happens when i try to use Akismet… Please help I have to get this site up by tomorrow for an interview im doing.
Thanks so much!