Use Database Mirroring Monitor tool to narrow down your problem. Refer the following link for further reference.
http://msdn2.microsoft.com/en-us/library/ms365809.aspx
http://msdn2.microsoft.com/en-us/library/ms365781.aspx
Also best practice:
http://www.microsoft.com/technet/prodtechnol/sql/2005/technologies/dbm_best_pract.mspx
Good Luck!
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"Thare are only 10 types of people in the world:
Those who understand binary, and those who don't."