How to find what is causing heap corruption (error 0xC0000374) in my Windows Store C# app?

My Win8 app started crashing out of blue due to a native exception. I then enabled the mixed (native + managed) debugger mode in VS and noticed the following:

• Before the app crashes, I get in the Output toolwindow the following message: Critical error detected c0000374.
• Then I get an Unhandled exception at 0x77DFAA3C (ntdll.dll) in MyApp.exe: 0xC0000374: A heap has been corrupted (parameters: 0x77E0FE38).
• When the debugger breaks, I get a "source not available" message and the stack trace info is not useful.

This seems to happen only when a Storyboard is running but that's just a wild guess. Any ideas how to rootcause what is causing the heap corruption?

PS: not sure if this is related at all, but I also noticed the following messages in the Output toolwindow before the heap corruption problem happens:

• First-chance exception at 0x75A84B32 (KernelBase.dll) in MyApp.exe: 0x40080201: WinRT originate error (parameters: 0x80004005, 0x00000026, 0x14E8F4F4).
• First-chance exception at 0x75A84B32 (KernelBase.dll) in MyApp.exe: 0x40080201: WinRT originate error (parameters: 0x80070490, 0x00000064, 0x05FFED2C). First-chance exception at 0x75A84B32 (KernelBase.dll) in MyApp.exe: 0x40080202: WinRT transform error (parameters: 0x80070490, 0x00000000, 0x0000001D, 0x05FFED58).
• First-chance exception at 0x75A84B32 in MyApp.exe: Microsoft C++ exception: EEMessageException at memory location 0x05FFD4F4.

Thanks!