Check Salesforce trust site http://trust.salesforce.com to make sure there are no issue with the Salesforce platform. Email normally process into Incidents in a less a minute, however Salesforce does not guarantee every email will be processed that fast.  Generally, speaking if an email has taken longer 30 minutes to process there is an issue somewhere.

The default Email Listener will not create an Incident unless it can match the From Address of the incoming email to an existing client or the Unidentified Client Setting is Configured in Remedyforce

Quick Steps to Test the Email Listener:
1. Verify the Email Listener is active.
2. Verify the Context user is active and it has Admin Profile and ServiceDesk Administrator permission sets associated to it.
3. Verify Error Routing is enabled.
4. Test the listener using the SFDC email address (this is the long email address associated with the listener).
5. Test the listener using the forwarding email address.
6. Verify the account associated with the listeners and the email address context user have Remedyforce licenses assigned to them.
7. Check new validation rules on the Incident object.  Validation rules on the creation of Incidents should contain below condition to allow incidents to be created by the listener.
 

(NOT(ISPICKVAL(BMCServiceDesk__contactType__c, "Mail Listen")

8.  In Remedyforce Administration | Configure Email | Incident - Email Settings check that both User to receive email processing error notifications and Client for unidentified sender are active if populated.

Staff/Client Email Verification:

1. Log to Remedyforce | Click Setup | Click Yes.
2. Under Administration Setup Expand Manage Users | Click Users.
3. Click the username of the user for which email is not processed.
4. Verify the email address is the same email address as the address the email is being sent from.

Remedyforce Configuration and Email Listener Troubleshooting:

1. Log into Remedyforce as Admin
2. Click Configuration | Click Application Settings.
3. Under General Verify the following:
Default Client Profile is configured with ServiceDesk Client.
Creating Incidents from Client Email is configured

NOTE: The default is set to required OPEN CALL in the email subject.  Open Call is NOT case sensitive.

Assign email-generated Incidents To: is set to Context User (Default).

4. Click Save | Click Ok.

Check the Email Listener:

1. Log into Remedyforce | Click Home | Click Yes.
2. Click the username | Click Setup.
3. Under App Setup Expand Develop | Click Email Services.
4. Under the Email Service Name column Click BMCSD CreateIncident.
5. Verify Settings are as required.
Apex Class is EmailListener.
 Accept Attachments is ALL.
 Accept Email From: is ALL email addresses (subject to security settings).
 Convert Text Attachments to Binary Attachments is checked.
 Active is checked.

6. If the above are not as desired Click Edit | Adjust accordingly | Click Save.
7. Under Email addresses Note the available email addresses.
8. Hover over the user in the Context User column.  Verify the user is active.
9. Beside the Email Address column | Click Edit.
10. Verify the Email Address Information in correct.
Active is checked. 
Context user is a valid user.
 Accept Email from is correct. - Whatever is in this box is the only email address from which the listener will accept mail.

   NOTE: Click the i in the upper right corner of the box for more configuration information.

11. Click Save.
12. Verify email can be sent to and is process by Remedyforce , i.e. and Incident is created.

For additional tips see Troubleshooting Remedyforce Email Services:
Troubleshooting Remedyforce Email Services - INCLUDES VIDEO