Here's another picture

http://forums2.gardenweb.com/forums/load/lawns/msg051546549734.html?8

Looking at pictures of dallisgrass it seems to look a little different than that.

Looks like crabgrass in the second picture. Second pic shows the turf is still thin. It will be a race between the bermuda and crab to fill those in.

How often are you mowing and how high/low?
How often are you watering and for how long?
Is there any shade in that area?
How often are you fertilizing and with what?

Dchall's right it's crabgrass. Use Drive (quinclorac) and the sooner the better will probably take a couple of apps. Next spring use a pre emergent herbicide to control. Crabgrass is easier to control with pre emergent than with post emergent herbicides.

Or if the OP starts following the Bermuda Bible (google it), he should have a very dense bermuda lawn that fully dominates other weeds.

I'm only home on the weekends, so I mow once a week. I usually cut about 1 3/4" and we have had soooo much rain lately that I haven't watered at all. I fertilized with Milorganite it late april, and that area is basically full sun.

I have a problem with this type of grass as well. It only pops up in high humidity months. It pushes out all other grass. Grows real thick. It is always wet might be 100 degrees out side but when you mow it is soaking wet. Makes a big mess after mowing. Is this grab grass? Looks the same as the picture only thicker.