If you have a VPS or dedicated server, you can login to SSH and run the command
Code:
cd '/home/[myusername]/public_html/[mydomainname]/lists/admin/' ; php -q index.php -p processqueue
and see what error you are getting.
Personally, I'd run a simple wget.
Code:
/usr/bin/wget -q -O /dev/null http://www.[mydomainname].com/lists/admin/index.php
I just don't know what you what switch you'd need to execute the "processqueue" part.