Over the last year we've seen several people report having performance problems when using F5 to run/debug ASP.NET 2.0 applications using Visual Studio 2005.  The problem in theses cases typically wasn't with building the project, but rather that it sometimes took the debugger a really long time to hit the first breakpoint once it attached to the application (45+ seconds and longer sometimes).

We recently posted a public hotfix patch that you can download and apply to fix this issue.  You can download the hotfix immediately here.  You can read more about it in this KB article here.

Source http://weblogs.asp.net/scottgu/archive/2007/08/21/public-hotfix-patch-available-for-vs-2005-f5-debugging-performance-issue-with-asp-net.aspx

Job done, this one had been 'bugging' me (get it)  recently.

Note: version of the Google Toolbar will also create problems, Remove it post haste!