Index: /trunk/src/VBox/VMM/VMMAll/PGMAll.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMAll/PGMAll.cpp	(revision 19789)
+++ /trunk/src/VBox/VMM/VMMAll/PGMAll.cpp	(revision 19790)
@@ -728,5 +728,7 @@
      */
     STAM_PROFILE_START(&pVCpu->pgm.s.CTX_MID_Z(Stat,InvalidatePage), a);
+    pgmLock(pVM);
     rc = PGM_BTH_PFN(InvalidatePage, pVCpu)(pVCpu, GCPtrPage);
+    pgmUnlock(pVM);
     STAM_PROFILE_STOP(&pVCpu->pgm.s.CTX_MID_Z(Stat,InvalidatePage), a);
 
Index: /trunk/src/VBox/VMM/VMMAll/PGMAllBth.h
===================================================================
--- /trunk/src/VBox/VMM/VMMAll/PGMAllBth.h	(revision 19789)
+++ /trunk/src/VBox/VMM/VMMAll/PGMAllBth.h	(revision 19790)
@@ -932,4 +932,6 @@
     PVM pVM = pVCpu->CTX_SUFF(pVM);
     PPGMPOOL pPool = pVM->pgm.s.CTX_SUFF(pPool);
+
+    Assert(PGMIsLockOwner(pVM));
 
     LogFlow(("InvalidatePage %RGv\n", GCPtrPage));