Receiving Error Msg when I log into my website

I just installed WordPress on my site through my cpanel, and I’m getting the following error message in 3 different sections when I go into my dashboard:

Not Acceptable
An appropriate representation of the requested resource /wp-admin/index-extra.php could not be found on this server.

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Apache/1.3.37 Server at sunkissedthoughts.com Port 80

What exactly does that mean? I’m very new to this whole website thing. Also, this error message is not allowing me to add categories when I go to compose a post. How can I correct this error message so it won’t show? Please help! Thanks.