EDIT: 1.4.x and below works fine.
Hey, I'm having big problems with Forge (1.5.x, I'll try with 1.2.5 after I posted this)
After installing Forge and launching the game, the little FML window does it's job, validates Minecraft and all the stuff it has to do, no errors there. I do not get any crashes or errors. But the thing is that the Mojang screen just stays there and nothing launches. I've let it opened for 10 minutes and got no results.
My specs:
Windows 7
2GB RAM (1.75 usable)
Java 6u45 (I also tried with Java 7u17)
If someone can help me with this problem, please leave me a message or comment, because I'd love to go play Ultimate Pack again, and try the new Tekkit.