webmatrix and nopcommerce debug not working

Hi All,
I installed Web Matrix and then installed the NopCommerce site from the web gallery. I set a break point in the default.aspx page_load but when I try to debug it skips the break point because it says "~no symbols loaded..."
When I pressed play button initially it asked if I wanted to enable debugging and I answered yes.
Am I missing something else?
 
Thanks,
 
rod.
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