Sounds like you've taken that +12 off a signal wire or something which can't provide the small current used by the stereo even when switched off. Try running a reasonable sized fused wire direct from your battery terminal.
If that doesn't work then maybe there is an internal short in your stereo, but if that was the case you probably would have blown fuses already.
Good luck, a bit of time with a multimeter usually solves these problems.
Hen
nah its the original 12v that goes to the stock headunit.
i did check it witht the multimeter before splicing and it was a constant 12v. watever happend, happened after i spliced it and connected the new head unit's connector. also it cant be a short in the stereo since i havent connected it to anything at all yet.