Single Roundcube user flooding server

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http://forums.cpanel.net – I am having a recurring issue where a single Roundcube user (not always the same) can flood the server with http requests. Server load slowly continues to increase over several hours, then abruptly drops back to normal levels (presumably because the user eventually closes the browser). /usr/local/cpanel/logs/access_log contains thousands of entries similar to these: Code: 91.143.xxx.xxx - - [11/09/2012:23:18:46 -0000] "GET /cpsess4647885551/3rdparty/roundcube/?_task=mail&_action=check-recent&_mbox=INBOX&_list=1&_quota=1&_remote=1&_unlock=0&_=135250312488 (HowTos)