I did some further test, it looks like this issue only happens on wx2.8 based C::B, my self build C::B which is wx3.1 based don't show this error message.
To test this issue, you can directly run threadsearch on the file "sdk\resources\lexers\lexer_powershell.sample". While, I also see that in my wx2.8, I can't open the file in the build-in editor, the editor just shows empty content. While under wx3.1 based C::B, I can correctly open the file under the buildl-in editor.