OpenCV Error: Unspecified error (The node does not represent a user object (unknown type?)) in cvRead... (Bug #4286)

Hi, all:

I'm testing OpenCV 2.4.11 these days, but met the following error message

OpenCV Error: Unspecified error (The node does not represent a user object (unknown type?)) in cvRead, file /home/ubuntu/Downloads/opencv/opencv-2.4.11/modules/core/src/persistence.cpp, line 5008

terminate called after throwing an instance of 'cv::Exception'
what(): /home/ubuntu/Downloads/opencv/opencv-2.4.11/modules/core/src/persistence.cpp:5008: error: (-2) The node does not represent a user object (unknown type?) in function cvRead

There seems to be such issue before, but non solutions work for me so far.
https://groups.yahoo.com/neo/groups/OpenCV/conversations/topics/72089

In addition, I still met the following issue:
OpenCV Error: Assertion failed (scn 3 || scn 4) in cvtColor, file /home/ubuntu/Downloads/ComputerVision/opencv/opencv-2.4.11/modules/imgproc/src/color.cpp, line 3739
terminate called after throwing an instance of 'cv::Exception'
what(): /home/ubuntu/Downloads/ComputerVision/opencv/opencv-2.4.11/modules/imgproc/src/color.cpp:3739: error: (-215) scn 3 || scn 4 in function cvtColor

Is 2.4.11 really a stable version??????????

Cheers
Pei