Can no longer install plugins

I have checked this forum and Googled this problem and found quite a few people complaining of the same thing, but nothing has yet solved the problem for me. I’ve been working on this site for a few days and it was working fine. Installed a few new plugins yesterday without a hitch.

But this morning, I went to install another plugin and could not successfully intall it. There seems to be a problem with the creation of folders during the process – I saw that someone with a similar problem was told to delete the “upgrade” folder and recreate it with 777 permissions, which I did, but that didn’t solve the problem. Now, I get a message that “folder already exists,” which refers to the folder for the specific plugin I’m trying to install. In the “plugins” folder on my cPanel, the folder does indeed get created. However, the wp-admin page doesn’t show it as installed.