This generally means that either a) the install of the web  part isn't correct or
b) the author of the web part is trying to do something that you as a user
doesn't have access to (via the web part).

First we probably need to know what web parts  you're talking about. Next, we
would need to know some information about your environment and the user adding
the web part ot the page to be able to deduce where the error might be.

Please check the GAC for dll, wpcatalog for dwp, web.config file for the web  part entry to make sure they have the same Version and PublicKeyToken.

There are a couple  of web  parts that we're trying to install. The first is a "Hello" web part:
store.bamboosolutions.com/p-20-hello-web-part.aspx

And the second is and RSS Reader:
www.aarnes.biz/.../Default.aspx


I'm the one who's actually trying to add the web part to the page. I'm an Administrator on the Sharepoint site. I didn't do the installation of the web parts  on the server. The person who did is away for a couple of weeks, so I can't say exactly how it was installed. These web parts are showing up in the Virtual Server Gallery on the Add Web Parts page.


If anyone knows of any other "Hello" web parts or RSS feed web parts, I'd be willing to give them a try......

Did you use STSADM.EXE to load the webpart or did you import it into the Gallery? This error usually refers to the fact that the webpart does not have a Safe Control entry in the Web.Config file for the site collection where it is being used. If that entry is there (it is created automatically if you install the webpart using STSADM.EXE) then the webPart is trying to do something that is not normally allowed, although I think this is usually a different message than the one you are getting.