EDIT: This is due to stupidity. It is a multiple monitor issue. It's just that from cmd.exe we always opened in the primary monitor, whilst from explorer, we always opened in the secondary. Thanks all for the help!
We hit a weird bug recently. We have a Qt + osg app that behaves differently if we run it from explorer than if we run it from a command line. Running from explorer is unusable, while running from command line (or by running from the explorer a simple batch file that calls the .exe) works as expected.
We suspect environment variables, because that's all we can think of. But the fact that it runs fine with a one line batch file seems to refute this. I'm not familiar enough with windows to know of any subtle differences in how it loads executables, nor where to look to find out.
Are there any other differences that could explain this? Does windows load different sets of user environment variables in each case? OS is Windows XP Service Pack 3.
The behavior experienced when running from explorer (double click program.exe) is consistent with a driver issue or improper OSG scene setup: image artifacts, flashing, and weird colors.
The behavior experienced when running the same executable from cmd.exe (or by double clicking a .bat file next to the .exe containing only a line to run the .exe) is the correct, expected behavior: the scene is correct, no flashing, etc.
To rule out potential library load path issues, try using dot-local DLL redirection.
Towards that end, create an (empty) file in the same directory as your executable and give it the same name as your binary, except with .local appended. I.e., if your binary is named yourbinary.exe, name that file yourbinary.exe.local. That will force the PE loader to first look in that directory to resolve LoadLibrary calls (and that includes DLLs loaded indirectly via system DLLs or via COM, no matter how many indirection levels are involved.) Place as many supporting DLLs (including Qt DLLs) in that directory. If you're using Qt plugins, also place the plugins directory there (or use a custom trolltech.conf.)
More details on dot-local redirection here, for example.