I'm also experiencing problems with this. All settings look correct.
In the file ./scp/cron.php i have no the following for testing:
$sec = time() - $_SESSION;
if($cfg->enableAutoCron() && $sec > 180):
//user can call cron once every 3 minutes.
Misc:('before Cron:();',"test");
Cron:();
Misc:('after Cron:();',"test");
Cron:();
$_SESSION=time();
endif;
The before email is perfectly sent, but it seem to "hang" on Cron:(); because the after mail is never sent.
Unfortunately I get no errors or anything, so it's hard to determine what is going wrong. But I get the feeling that the POP3 function in the file ./include/class.cron.php is never reached at all. Because I have tried a few logging functions inside the POP3() function, but none of them worked/are called.
Any suggestions??