I did a google.com search but didn't find any information specifically geared to your question. I did find this bit of information and a website:

From smallfruits.org:

Growers should delay pruning as late as possible in the winter. Do not prune the vines from late November through mid-January if possible. Pruning done at this time has resulted in considerable winter injury and vine death. Although late pruning results in heavy bleeding, there is little evidence that bleeding is harmful.

More how-to here:

http://homeguides.sfgate.com/time-year-prune-muscadine-grape-vines-44962.html

Hi Robin, I have no ide as to your grape question, but are you going to Silvia's garden party? You are welcome to ride with me if you'd like!

I did the same thing with my grapes (Not muscadines) and am kicking myself, too. I actually intended to get mine cut WAY back to start espilar..oK I can't spell but now that they are green again I don't dare. Actually because of this I will probably never move them now and they'll end up just taking ove the structure they are on. BAD ME! I'll just get new vines to play with and prune properly I suppose. ;-) (excuse, perhaps?)

Mine have already put on a few flowers so I'd worry that you won't get fruit or much if you trim now.

Thank you all for responding ! My computer or maybe its my server HATES this site. I have so much trouble doing anything on gardenweb since Spike turned it over. Today is my first time to be able to see this post since I posted it last weekend, Uggh. SOooooo the vines leafed out a lot very quickly so I figured I better just leave them alone. Barbi I would love to compare notes on how yours do. I forget how far north of me you are?? I am in Cape Coral.

Mrs tlc I would have LOVED to carpool with you! I wanted to go but dh couldn't go and I didn't want to make the trip alone. Pictures?

Oh Robin, I wish I'd have been able to get in touch. I sent you an email but it got returned so I posted here in hopes you'd see it in time. Let's try next time :)

I didn't take any pictures. I was going to but just got so caught up in enjoying meeting and talking to people....LOL I know some did so we will probably see them soon.

I am 1 exit North of Lori's house near Tampa. (Didn't I see you there once?) If not then we spoke of meeting there and it fell through, perhaps. So about 2.5 hours North from you? Depending on what side of Cape Coral you are on. My vines are nearly completely leafed out now.

I've got concord and....? Oh, I can't remember the other type now. Something that is 'supposed' to be OK for around here, but you know how that goes. Florida is notorious for death by fungus.

I have muscadines as well It's not too late to prune them. Just don't prune the one year old wood too heavily. This years growth is what should fruit this year. Not sure if that makes a lot of sense. I would go ahead and prune anything of last year's growth that is not following or already attached to your trellis wires. Not pruning is actually more likely to result in less fruit in the long run than pruning too much believe it or not. If you don't prune the vine is more likely to concentrate on vegetative growth and may not have enough energy or the ability to provide enough water for an abundant fruit harvest.

Forgot to mention I actually prune back new growth several times prior to flower budding to ensure good air circulation on the fruit later in the season. And continue to knock back purely vegetative growth for the same reason throughout the growing season.