After logic board replacement my MBP boots to a black screen......

single user mode and verbose mode should not be 'toggles', there are key combinations that cause it to do that (typically, not sure about orcinus' trick, though i know fedora has a similar text vs gui line you can edit, but i'm getting off topic), meaning if you hold 'v' to go verbose mode, when you reboot, it shouldn't do the same thing (unless you hold 'v').... when you boot to the os, do the 'v' and 's' keys work normal or do maybe seem stuck?
try reseting your pmu and pram (unplug from power, remove battery hold down the power button for 10 seconds; then hold apple option+pr while booting the computer until you hear a second startup chime)
are you running bootcamp??

Hi Dakavo,

First try resetting your PRAM by restarting your MacBook Pro and holding down "Command", "Option", "P", and "R" at the same time. Continue to hold them down until you hear the startup chime sound twice, then release the keys. More info is found here:
http://docs.info.apple.com/article.html?artnum=2238

If that doesn't work then check to see if you have a firmware update. You can find out by connecting to the internet and clicking on the Blue Apple logo in the top left corner and choosing "Software Update". If you do then please download and install it. More info is found here:
http://docs.info.apple.com/article.html?artnum=303880

If these don't work then my recommendation would be to take the unit into an Apple Authorized Service Provider or Apple Retail Store. Or you can call 1-800-APL-CARE for phone assitance.

Derek C.