leak under dash

I've got a 2008 Chevy Cobalt. I bought it in May 2010. Great car until this recent problem.

In Nov 2011 a leak started up under the dashboard.
I called the dealer, thinking just maybe it would still be under warranty. It wasnt, but they convinced me I should take it there since it was a 'water' problem.

They replaced a bracket and a filter. description said "replaced cabin filter and clear cowl drains." $270.48

They said, they hoped that fixed it. its possible the water had damaged (something... dont remember exactly but i think they meant that round black 'thing' under the dashboard that the water was dripping out of. blower motor maybe?)

well almost 4 months later - same thing. Took it to a different auto repair shop cause I figured the dealer would just rip me off (again... cause thats what I felt like happened).

They charged 96.85 diagostic fee, $96.85 labor and $17.05 for a cabin air filter. total $246.36. i thought surely they mistakenly charged me double! but didn't.

What they did was replaced cabin air filter, repair fitting at the a/c drain, R&R cowl panel and clean A/C drain. They suggestion for it not to happen again was to "go thru the car wash once a week."

What i'm wondering is -
Could this be a defect?
do others have this problem?
is that REALLY the solution? go thru the car wash once a week? sure a clean car is nice, but i shouldn't HAVE to go thru the car wash once a week to keep from something getting stopped up and causing a leak inside my car that i have to pay over $200 to get fixed on a regular basis!

Is the wet spot water or is it kinda slimy like coolant?? Ive seen some problems where heater cores leak and they will leak inside but other wise i have no idea where else it could be leaking from

when you turn on your heat, do you smell coolant really bad?

It didn't smell until after the floor stayed wet for 2-3 days. and its not slimy.
i'm going to try to lift up the cowl (not tonight) and look under it and see if i can see what drain that might be getting stopped up and if i do maybe i can just go make sure its not getting stopped up with debris every so often, especially when there is so much pollen and sticky stuff all in the air and falling from the trees.

Got a sunroof? The drains are known to get plugged and/or disconnect.

Sounds like water.

If it leaks worse after using either side of the A/C (hot or cold), I would start there. If the A/C system has no effect on it, I would look into trims/sealers (your window trim/seal for example).

I have a 2010 that leak from the seal on the roof under one of the rubber trim.Had it at the dealer in Canada and they checked the windshiel seal.Went to florida and hit rain on the way,got soaked on driver side,it's running down the corner post by the windshield.They kept in 2 days at dealer in Florida,resealed the roof seam and changed the rubber molding on roof .Coming back hit heavy rain on I-75 got soaked again.Goin back to dealer in Canada monday.