On the command line window where I start MegaGlest from, lines like these are printed every ~ tenth of a second on Windows 7 Home Professional running in Virtualbox virtualization. This may be just due to the imperfect video virtualization...
[..\..\source\shared_lib\sources\graphics\gl\font_textFTGL.cpp::Shared::Graphics::Gl::TextFTGL::Advance] Line 262 Error = 1280 [invalid enumerant] for text [http://megaglest.org]
[..\..\source\shared_lib\sources\graphics\gl\font_textFTGL.cpp::Shared::Graphics::Gl::TextFTGL::LineHeight] Line 313 Error = 1280 [invalid enumerant] for text []
The first one is printed during the intro (when the URL displays on screen), the second is in the About menu. Depending on which menu you're in the message changes slightly, as does the text presented in square brackets.
Edit: Further discussion on IRC indicated this is in fact just due to shortcomings in the video virtualization.