C0000005 coming from Unbindevents

[AlastairP]

I have been experiencing occasional c5 errors.
The VFP9Rerr.log keeps referring to BindWindowsEventsProxy.Destroy line 4, which is "Unbindevents(_vfp.HWnd, WM_THEMECHANGED)"

#Define WM_THEMECHANGED        0x031A

If Type("This.Parent") # "O" Then
   Unbindevents(_vfp.HWnd, WM_THEMECHANGED)
Endif

Sometimes when I get the c5 errors, there are additional lines in the VFP9Rerr.log prior to the BindWindowsEventsProxy.Destroy line 4, that refer to the "propershutdown" function in the main.prg.
These line numbers are in every case calling _vfp.startmode

IF _VFP.STARTMODE = 0 <- Line number referenced in error log
[indent]...[/indent]
ENDIF

This class BindWindowsEventsProxy is in vfpx.vcx which appears to be part of the ctrl32 library