iLast.Fm provides a complete integration between your blog and your Last.fm account, show what musics you are listening to and much more!
This probably happens because the folder /cache (inside of /ilastfm) doesn't can be writable. To solve this problem, use an FTP, go to folder cache and try put CHMOD 775.
Go to iLast.Fm Options and simply click in "Save Settings". Done.