Cannot debug .NET-based PowerPoint add-in

I have a PowerPoint add-in developed with .NET Framework 4.0/C#/VSTO. The add-in loads fine when I manually launch PowerPoint, but when I press F5 in Visual Studio, the PowerPoint splash screen shows for a short period and then PowerPoint closes. The Visual Studio output window shows only the following lines:

'powerpnt.exe' (CLR v4.0.30319: DefaultDomain): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_32\mscorlib\v4.0_4.0.0.0__b77a5c561934e089\mscorlib.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled. The program '[6016] powerpnt.exe: Program Trace' has exited with code 0 (0x0). The program '[6016] powerpnt.exe' has exited with code -2146233082 (0x80131506).

I've tried the following:

• HDD scan
• reinstalled VSTO

Do you have other suggestions to fix this issue?

I've uninstalled EMET 4.1 and, after a few reboots of the system, I've been able to debug again. Now I cannot say for sure that EMET was the culprit, since I've been able to debug before with EMET installed. I'll install EMET back when possible.