When you log in to the email account WHD is monitoring, the email is there? If WHD is not processing the email, it should still be in the inbox. If it is not, I'd have a window open to that account, and send an email there, to ensure it is arriving. Those are the first two steps I follow when I'm troubleshooting.
sunnymcduff, I bet the software cleaned up email history entries, but didn't clean up the corresponding email_data_object. What do you get when you run the following sql: select * from email_data_object where email_history_entry_id = 110138. If anything is returned, the join fails and the software displays an error. I bet you see errors in the helpdesk.log file saying something like 'Could not find email_data_object with history_entry_id with id 110138' or something to that affect. Errors like these come up because of the referential integrity built into the database.