Sometimes black screen during boot, cycling sleep/wake works

I have this Macbook from 2008, with Intel graphics. Some time ago I begun having troubles with the backlight, it would shut down after some time usually when at highest setting.

I replaced the backlight and now the backlight does not shut down in use which is of course good thing, but now new type of problem has appeared. The machine sometimes boots to black screen and continues to load into Mac OS X. If I put the machine to sleep and wake it up again the light comes back. During normal use there are no problems, no flickering etc.

So at the moment problems only during start up. Does this sound like the motherboard is having problems, or inverter or did I screw up something during installation? It could be all, this was my first backlight replacing fix and it wasn't that easy, atleast for me.