Initially, everything was working fine for a couple of months. Recently, though, I've been consistently getting these exceptions when working in the XAML designer. When I first open an XAML document, the designer loads as usual, but once I click on a particular control, the exception is thrown. Reloading the designer does just that, but the exception is still thrown when clicking on that control. The message associated with the exception is:
Value cannot be null.
Parameter name: sp
Originally, I thought this was only occurring with controls which were either custom controls or which I had applied a style to. However, some styled controls work fine in the designer, while other built in controls do not.
I should note that my project compiles absolutely fine. No build errors are reported and the build succeeds. No exceptions are thrown at runtime, nor do I see any unexpected results in terms of styling and functionality.
I have this problem on two separate PCs. Both run Visual Studio 2012 Professional. One PC runs Windows 8 Professional and the other Windows 8 Enterprise. Neither version of Windows 8 is a preview or RC, they both are the actual releases.
I've attached the data from three logs in the Event Viewer for a particular occurrance.