Hey, I just saw this thread while lurking. I used to work for a waterproofing company that worked only with homeowners (i.e. not new construction). I worked there for two years, and this was a reputable family owned company.

What I can tell you is this: when groundwater is getting into your basement, there are few "quick" or cheap fixes. The problem is highly variable depending on (among other things) pre-existing waterproofing / drainage, the slope of the land, type/size/shape of foundation, obstacles around the exterior of the foundation, etc.

Unfortunately the company I worked for was in North Carolina, so are not a contracting option (and it is true that there are many shady / disreputable people); but, LWP often got calls from people out of state just asking for advice, and their website offers a lot of good information. They even have an Info Series of fact pages. You could check out their website for some information about common groundwater issues:

http://www.lindsleywaterproofing.com

Good luck!

JEG