Windows 8 で次の例外が発生します。ただし、Windows 7 環境では動作します。この例外は comctl32.dll によってスローされるようです。コンボボックスではなくツールチップに問題がある以下を調べました。
COMCTL32.dll を失敗させる ToolTip の AccessViolationException - .NET 4.0
アプリケーション: Application.exe フレームワーク バージョン: v4.0.30319 説明: 未処理の例外が発生したため、プロセスが終了しました。例外情報: System.AccessViolationException
at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr, IntPtr, Int32, IntPtr, IntPtr)
at System.Windows.Forms.NativeWindow.DefWndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control.DefWndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control.WmCommand(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.ComboBox.WndProc(System.Windows.Forms.Message ByRef)
at CCS.UserInterface.MetaComboBox.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control+ControlNativeWindow.OnMessage(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control+ControlNativeWindow.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.NativeWindow.Callback(IntPtr, Int32, IntPtr, IntPtr)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG ByRef)
at System.Windows.Forms.Application+ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr, Int32, Int32)
at System.Windows.Forms.Application+ThreadContext.RunMessageLoopInner(Int32, System.Windows.Forms.ApplicationContext)
at System.Windows.Forms.Application+ThreadContext.RunMessageLoop(Int32, System.Windows.Forms.ApplicationContext)
at System.Windows.Forms.Application.Run(System.Windows.Forms.Form)
at <Application>.MainApplication.Load(Splash)
at <Application>.Program.Main(System.String[])
Faulting application name: CCSEnterprise.exe, version: 4.354.4.15321, time stamp: 0x53dfe4c1
Faulting module name: comctl32.dll, version: 6.10.9600.17031, time stamp: 0x5308889d
Exception code: 0xc0000005
Fault offset: 0x00051a6e
Faulting process id: 0x13f8
Faulting application start time: 0x01cfb08bc91cf716
Faulting application path: C:\355AAA\Application.exe
Faulting module path: C:\WINDOWS\WinSxS\x86_microsoft.windows.common-controls_6595b64144ccf1df_6.0.9600.17031_none_a9efdb8b01377ea7\comctl32.dll
Report Id: 2284a19e-1c7f-11e4-be73-1078d298a609
Faulting package full name:
Faulting package-relative application ID: