I'm not sure i have anything to add here that is new, but I had to read the thread because here in northern NJ, i haven't seen my grass for weeks. We still have close to a foot of snow on the ground.
If the grass you are looking at is not dying and starting from zero every year, it may not be crabgrass. There is a very similar, clumpy-growing grass called goosegrass.
If you have a very widespread problem, a pre-emergent weed killer is probably your best bet. But all the major commercial brands will instruct you to wait until the fall to reseed...not a very desirable situation. It may be worth your time to get a spot spray weed killer and just walk around once a week and shoot the bad guys. You won't have to wait so long to reseed, and you may find it is more economical than a full lawn's worth of the spreadable stuff. It is supposed to be more ecological too, because there is way less run-off.