Our windows are now 5 years old. They are the large classic double hung windows. In the last few months the carpet has been getting wet. So, today the builder returned. He remove the inside trim and we found that in the bottom corner of each window at the 'welded' 45 angle, that it had seperated. So, during rains, the water escaped thru the outside weep holes as normal as well as thru each weld that had cracked. Since this is at the bottom of the window and under the inside window trim/sill, we had no way to see this.
The builder said he had seen this before with the MW Windows. He is replacing the windows and is 'not going to mess with MW Windows. Interesting. Thanks Lennnar!