I develop WPF applications using Visual Studio 2012. Yesterday morning I installed Spybot S&D 2.2 free edition, updated and performed a system scan. For the rest of the day WPF applications were taking MUCH longer to launch. Whether started from within Visual Studio or directly from Explorer, any WPF application that I started would take upwards of 6 seconds to appear on the screen.

At this point, I had no idea Spybot was the problem, and I spent all afternoon Googling "slow WPF application startup" and trying all the fixes suggested. Nothing worked. I realised Spybot might be scanning the files and assemblies used by WPF apps as they were loaded and thus slowing down the process, so I disabled the file-access scanning functionality of Spybot (or at least tried to). No change.

On a whim, I uninstalled Spybot and rebooted, and magically WPF startup speed was back to normal! Even from within the debugger, apps that took 6 seconds to start yesterday are now taking 1/4 second to start.

So, why would Spybot be causing such a slowdown? Is there any way I can keep Spybot installed and active without this huge speed hit?