LPLWeb on "500 error won't resolve."

I encounter this error on my ftp when I attempt to rename the active theme's directory:

Command: RNFR remobile-pro
Response: 550 Access is denied.

I've access to an error log but am unsure as to what you may be looking for. I did find this bit of the report that I thought may be relevant:

GET /wp-includes/SimplePie/HTTP/404_error.php