diff -r a528b32f5195 src/cl_demo.cpp
--- a/src/cl_demo.cpp	Thu Aug 08 20:27:16 2013 +0200
+++ b/src/cl_demo.cpp	Thu Aug 08 20:56:37 2013 +0200
@@ -99,6 +99,9 @@
 // Our byte stream that points to where we are in our demo.
 static	BYTESTREAM_s		g_ByteStream;
 
+// [BB]
+static	BYTE				*g_pbMarkedStreamPosition;
+
 // Name of our demo.
 static	FString				g_DemoName;
 
@@ -400,33 +403,25 @@
 
 //*****************************************************************************
 //
-void CLIENTDEMO_InsertPacket( BYTESTREAM_s *pByteStream, BYTE *pPosition )
+void CLIENTDEMO_InsertPacketAtMarkedPosition( BYTESTREAM_s *pByteStream )
 {
 	// [BB] We can write to the current position of our stream without any special treatment.
-	if ( pPosition == CLIENTDEMO_GetDemoStream()->pbStream )
+	if ( g_pbMarkedStreamPosition == CLIENTDEMO_GetDemoStream()->pbStream )
 		CLIENTDEMO_WritePacket( pByteStream );
 	// [BB] If we are supposed to write to a previous position, we have to move what's already there..
-	else if ( pPosition < CLIENTDEMO_GetDemoStream()->pbStream )
+	else if ( g_pbMarkedStreamPosition < CLIENTDEMO_GetDemoStream()->pbStream )
 	{
-		// [ZZ] Preserving the position that may possibly change during clientdemo_CheckDemoBuffer
-		//      this assumes that pPosition is more or equal to demo buffer beginning
-		int oldPos = pPosition - g_pbDemoBuffer;
-
 		// [BB] Save the stuff currently at the desired position.
-		const int bytesToCopy = CLIENTDEMO_GetDemoStream()->pbStream - pPosition;
+		const int bytesToCopy = CLIENTDEMO_GetDemoStream()->pbStream - g_pbMarkedStreamPosition;
 		BYTE *copyBuffer = new BYTE[bytesToCopy];
-		memcpy( copyBuffer, pPosition, bytesToCopy );
+		memcpy( copyBuffer, g_pbMarkedStreamPosition, bytesToCopy );
 
 		// [BB] Make sure we have enough space for the new command.
 		clientdemo_CheckDemoBuffer( pByteStream->pbStreamEnd - pByteStream->pbStream );
 
 		// [BB] Change our demo stream to the desired position and write the incoming packet there.
-		// [ZZ] Restore the old position.
-		//      Is this needed at all? See this (clientdemo_CheckDemoBuffer):
-		// 		lPosition = g_ByteStream.pbStream - g_pbDemoBuffer;
-		//      g_pbDemoBuffer = (BYTE *)M_Realloc( g_pbDemoBuffer, g_lMaxDemoLength );
-		//      g_ByteStream.pbStream = g_pbDemoBuffer + lPosition;
-		CLIENTDEMO_GetDemoStream()->pbStream = g_pbDemoBuffer + oldPos;
+		// [BB] clientdemo_CheckDemoBuffer updates g_pbMarkedStreamPosition if necessary.
+		CLIENTDEMO_GetDemoStream()->pbStream = g_pbMarkedStreamPosition;
 		CLIENTDEMO_WritePacket( pByteStream );
 
 		// [BB] Append the saved stuff.
@@ -443,6 +438,13 @@
 
 //*****************************************************************************
 //
+void CLIENTDEMO_MarkCurrentPosition( void )
+{
+		g_pbMarkedStreamPosition = CLIENTDEMO_GetDemoStream()->pbStream;
+}
+
+//*****************************************************************************
+//
 void CLIENTDEMO_ReadPacket( void )
 {
 	LONG		lCommand;
@@ -849,9 +851,13 @@
 		// Give us another 128KB of memory.
 		g_lMaxDemoLength += 0x20000;
 		lPosition = g_ByteStream.pbStream - g_pbDemoBuffer;
+		// [BB] Convert our marked position to an offset.
+		const LONG markedOffset = g_pbMarkedStreamPosition - g_pbDemoBuffer;
 		g_pbDemoBuffer = (BYTE *)M_Realloc( g_pbDemoBuffer, g_lMaxDemoLength );
 		g_ByteStream.pbStream = g_pbDemoBuffer + lPosition;
 		g_ByteStream.pbStreamEnd = g_pbDemoBuffer + g_lMaxDemoLength;
+		// [BB] Restore the marked position based on the new pointer.
+		g_pbMarkedStreamPosition = g_pbDemoBuffer + markedOffset;
 	}
 }
 
diff -r a528b32f5195 src/cl_demo.h
--- a/src/cl_demo.h	Thu Aug 08 20:27:16 2013 +0200
+++ b/src/cl_demo.h	Thu Aug 08 20:56:37 2013 +0200
@@ -89,7 +89,8 @@
 void		CLIENTDEMO_WriteTiccmd( ticcmd_t *pCmd );
 void		CLIENTDEMO_ReadTiccmd( ticcmd_t *pCmd );
 void		CLIENTDEMO_WritePacket( BYTESTREAM_s *pByteStream );
-void		CLIENTDEMO_InsertPacket( BYTESTREAM_s *pByteStream, BYTE *pPosition );
+void		CLIENTDEMO_InsertPacketAtMarkedPosition( BYTESTREAM_s *pByteStream );
+void		CLIENTDEMO_MarkCurrentPosition( void );
 void		CLIENTDEMO_ReadPacket( void );
 void		CLIENTDEMO_FinishRecording( void );
 void		CLIENTDEMO_DoPlayDemo( const char *pszDemoName );
diff -r a528b32f5195 src/cl_main.cpp
--- a/src/cl_main.cpp	Thu Aug 08 20:27:16 2013 +0200
+++ b/src/cl_main.cpp	Thu Aug 08 20:56:37 2013 +0200
@@ -1290,7 +1290,7 @@
 		commandAsStream.pbStreamEnd = pByteStream->pbStream;
 
 		// [BB] Memorize the current position in our demo stream.
-		BYTE *pbDemoStream = CLIENTDEMO_GetDemoStream()->pbStream;
+		CLIENTDEMO_MarkCurrentPosition();
 		lCommand = NETWORK_ReadByte( pByteStream );
 
 		// End of message.
@@ -1314,7 +1314,7 @@
 		{
 			// [BB] Since we just processed the server command, this command ends where we are now.
 			commandAsStream.pbStreamEnd = pByteStream->pbStream;
-			CLIENTDEMO_InsertPacket( &commandAsStream, pbDemoStream );
+			CLIENTDEMO_InsertPacketAtMarkedPosition( &commandAsStream );
 		}
 
 	}