Problem with PDF Text

I have just installed Omeka 2.0.4 on Bluehost. I am trying to install the PDF Text plug-in without success. When I click on Install it 'whirs' as though installing, but when the screen refreshes the green Install button is still present. No error message and nothing in the error log. I tried removing it and uploading a fresh zip file from the site, extracting and repeating the process, but no change. Please advise.

Since you had difficulty with Commenting, too, I'm wondering if this is a broader problem in the installation. Have you been able to install other plugins, like the bundled Simple Pages or Exhibit Builder?

Yes, I was able to install several other plugins with no apparent problems, including the three that came with the Omeka download.