Do you research before doing any drinking with diabetes!
As mentioned above the issue arises when the liver is forced to handle alcohol, it sort of sees the alcohol as toxic and puts all of its other duties on hold to deal with this. Doing this means it no longer puts out glucose, or much less of it, and since our pancreas can't adjust the insulin levels for us our normal basal injection is too much insulin and we go low. If you are on a pump you can lower this basal rate to match, but on injection you cannot.
So now your liver and pancreas are pretty much out of the picture, anything you eat wont do much to raise your sugars if you still have alcohol to process. Many people find that even the following day your liver still isn't back to normal and they go low many hours after drinking.
If you eat and inject while drinking / drunk you may find that your normal I:C ratio is out of whack and you end up going low because the insulin will still work as per usual, but the liver wont process the carbs as you expect it too.
Drinking more then 2-3 drinks is something i have yet to master, and after the first failed attempt doubt i will try again until i get a lot of experience with my pump..