Is your logo.png a size of 2... like 256x256 or 512x512 or 1024x1024. Try tgat.
It could be your problem.
Otherwise it could be your bloody_menu.map OR even the name of it.
You can also check your .hpl log, you can find it on MyDocuments/Amnesia.
Look it up and be free to post it here.
Try adding it in a spoiker tag.
And..or
You can also try .tga or .dds in stead of .png.
Try these small and easy things first.
After that we can help with looking more into your .hpl error logs and maps and config files.