Question
Hi once again Kenneth, I'll try to be brief.  Killed everything last fall;  lots of burmdua grass - 3 applications of round-up.  Location in Chesapeake, VA, mild weather.

Did soil sample, pre-fertilized soil with recommended nutrients, worked it in, seeded and over-seeded with Rebel.  Slow germination, but looked pretty good after a while.  Built in irrigation.  Mild, Mild weather right now and spurge is out of control.  Purple flowers right?  Just applied weed-b-gon via post mix system with a garden hose.  Grass suvived well, but spurge did too.  This weed is definitely actively growing because it's flowering, temps in high 50's.  Can I do something else before spring?  I'd like to be weed free.

Signed;  Lota work, crappy yard

Thanks   Randy P

Answer
Spurge ?
Spotted spurge and creeping spurge are the most common..

http://www.ipm.ucdavis.edu/PMG/WEEDS/spotted_spurge.html
http://www.ipm.ucdavis.edu/PMG/WEEDS/creeping_spurge.html

Could it be:
Ground Thistle, Dwarf Thistle (Cirsium acaulon)
Henbit (Lamium amplexicaule)
Herb Robert (Geranium robertaianum)
Cranesbill (Geranium spp)
Self Heal (Prunella vulgaris)
Kenilworth Ivy, Ivy-leaved Toadflax (Cymbalaria muralis)
Purple loosestrife (Lythrum virgatum and hybrids)

Take a look here for ideas:
http://dnr.metrokc.gov/wlr/lands/weeds/weedid.htm

In any event, don't worry about the weeds now. The weeds which can be controlled via selective herbicides (post emergent sprays) will be best treated later.

First step is proper identification.

Once that is done, feel free to ask again...

(I know that weeds can be very hard to idenfity, but it does make eradication easier at a later stage)