[ahampton2k]

I was having some trouble with getting mail on my phone in the evenings, come to find out that if you run live messenger it locks blackberry service out from checking the inbox.

Here is the RIM documentation:

Overview
Email messages are not received in real-time to the BlackBerry smartphone when a BlackBerry Internet Service subscriber has the following environment:

The computer is running Windows XP
A Windows Live Hotmail account is integrated with the BlackBerry Internet Service account
Windows Live Messenger (previously known as Microsoft� MSN� Messenger) on the computer is being used
Note: This issue does not occur when an earlier version of Windows Live Messenger is used in this environment.



Cause
Windows Live Messenger and BlackBerry Internet Service both use the Microsoft Notification Protocol (MSNP) to receive notifications for new email messages.

MSNP is designed to notify only one application at any given time. If the Windows Live Messenger application is active, a notification of the new email message appears in the Windows Live Messenger application on the computer. If Windows Live Messenger is inactive, the MSNP sends a notification to the BlackBerry Internet Service and the email message is sent to the BlackBerry smartphone in real time.



Resolution
This is by design.

Install Windows Live Messenger for BlackBerry smartphones.

Note: Windows Live Messenger for BlackBerry smartphones does not receive new email notifications and will not compete with BlackBerry Internet Service for the notifications from the Windows Live Hotmail service.



Additional Information
The BlackBerry Internet Service will begin receiving the new email notifications when Windows Live Messenger on the computer goes into an inactive status.


Products
BlackBerry Internet Service
Windows Live Messenger
Source: View Document

[MitchB711]

I am experiencing this issue too. Started for me about a week ago.

[ahampton2k]

I stopped using messenger since i posted this and have not had any problems since.