Here is a message to FBF,
ok, i suspect your mirror kinda shifted, so
open your window on a nice sunny day point the camera towards the outside, look for a tree, a building or a hot nude model, ( i have one when i open my window so..) that is far far away at infinity and set it there.
take a screwdriver take the top plate out.
use a really small, ( i donno what driver it is called almost like a pin)
set your camera to infinity and start twisting the points one by one "SLOWLY" it will break your glass if you over screw it.
i dont recall but there are 1 for tilting left and right, there is one for up and down and one diagonally? looser goes up? tighter goes down, maybe. dont remember.
do this slowly until your setting to infinity is perfect and it looks perfect in the finder too.
you can either put some light bond(weak glue) (save you time getting it off in the future) or just leave it as it is, until next time when it doenst sync nicely then you repeat the process.
after that close the top plate and you are ready to dance.
hope this helps, if its some other major camera body problem, then as advised above, look for a cheap second hand body and replace the front unit..