I have a web application that I've always been able to run in Visual Studio and it debugs just fine (breakpoints work, I can pause execution, etc). Recently, the behavior changed suddenly, and a few things happen:

• I start debugging, it lauches IE and loads the application, but after a few seconds (sometimes the page hasn't even displayed yet), Visual Studio acts as if debugging has stopped - I'm able to edit code in VS again, and the "Play" button on the toolbar is enabled. The application continues to run in the IE window just spawned, but I'm not attached to it
• During this few seconds that VS is "debugging", because it detaches, my breakpoints show as hollow - as if I'm set to "Release" mode and they won't be hit. In fact, I have a breakpoint set in Page_Load, and it skips right by. I've checked, and I'm set to debug mode, though the compile mode dropdown is missing from my toolbar (I checked in the build properties to ensure I was in debug mode).

Can anybody shed some light here?