Exception

[durongze]

MergeGui.vshost.exe' (CLR v4.0.30319: ILMergeGui.vshost.exe): Loaded 'C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.XML\v4.0_4.0.0.0__b77a5c561934e089\System.XML.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ILMergeGui.vshost.exe' (CLR v4.0.30319: ILMergeGui.vshost.exe): Loaded 'C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Xml.Linq\v4.0_4.0.0.0__b77a5c561934e089\System.Xml.Linq.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ILMergeGui.vshost.exe' (CLR v4.0.30319: ILMergeGui.vshost.exe): Loaded 'C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\mscorlib.resources\v4.0_4.0.0.0_zh-Hans_b77a5c561934e089\mscorlib.resources.dll'. Module was built without symbols.
The thread 0x494 has exited with code 0 (0x0).
The thread 0x14ec has exited with code 0 (0x0).
'ILMergeGui.vshost.exe' (CLR v4.0.30319: ILMergeGui.vshost.exe): Loaded 'D:\code\ILMergeGUI-master\ILMergeGui\bin\Debug\ILMergeGui.exe'. Symbols loaded.
'ILMergeGui.vshost.exe' (CLR v4.0.30319: ILMergeGui.vshost.exe): Loaded 'C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Configuration\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Configuration.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ILMergeGui.vshost.exe' (CLR v4.0.30319: ILMergeGui.vshost.exe): Loaded 'C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\Accessibility\v4.0_4.0.0.0__b03f5f7f11d50a3a\Accessibility.dll'. Cannot find or open the PDB file.
Exception thrown: 'System.Security.SecurityException' in mscorlib.dll

[jpdillingham]

Take a look here: #1

Please try to run under and administrative account and see if that resolves it.