The long story is convoluted, so I'll sum it up as this:
1. I had LU working just fine a few months ago, not sure if it was under Windows 7 or Windows XP.
2. I have the exact same .exe and the exact same conditions, just a different version of LU.
3. The .exe works fine by itself and is considered valid by LU, but the .exe refuses to give me the "Welcome to Liberty Unleashed" red-tinted loading screen or actually connect to a server.
The .exe itself is some no-CD crack I picked up years ago and have been using ever since with the Steam version of GTA3 (to fix the all-cars-are-yellow glitch, and to allow for modding). Any ideas?