VS2005 Strange: The breakpoint will not currently be hit. No symbols loaded for this document.

I can't debug a Web Application with VS2005.
I can insert a brakpoint on any class, but I can't debug any page.
An breakpoint on a page code results in the error:

The breakpoint will not currently be hit. No symbols loaded for this
document.

I have searched on internet for more than 2 hours, but nothing solve my
problem.
I ran aspnet_regiis -u then aspnet_regiis -i
I recreate the application on IIS mmc
I deleted any file on
C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files
I don't know if is a problem of the configuration of the project or a
configuration of the machine.

Please, help me, because I don't know what I have to do anymore.

Thanks a lot.

Roberto