Problems with importing texture to UT

I follow all the rules of importing texture to UT, (change the format of the texture to TGA and 256x256 in Photoshop). I saved the texture into the package "myLevel", however, the computer come up with "Build UT2004_Build_[2005-11-23_16.22]
OS: Windows XP 5.1 (Build: 2600)CPU: GenuineIntel PentiumPro-class processor @ 2674 MHz with 2047MB RAMVideo: NVIDIA GeForce 8600 GT (6367)
Assertion failed: GObjBeginLoadCount==0 [File:.\UnObj.cpp] [Line: 2295]
History: UObject::StaticTick <- UEditorEngine::Tick <- UpdateWorld <- MainLoop" dont know what happened!!! That's why i can not add texture to my model.